Unwanted random semicolon between some names in citation

Question

I have a quite complicated template to write my thesis with, however there is a small issue that I cannot solve. The majority of the citations in my text (using ISO 690:2010 standard and the biblatex-iso690 bibliography style) are fine, however some have an interesting issue with the authors' names.

Example of a good .bib entry:

@article{dewach06,
    ISSN = {00222879, 15384616},
    URL = {http://www.jstor.org/stable/3839071},
    author = {Hans Dewachter and Marco Lyrio},
    journal = {Journal of Money, Credit and Banking},
    number = {1},
    pages = {119--140},
    publisher = {[Wiley, Ohio State University Press]},
    title = {Macro Factors and the Term Structure of Interest Rates},
    volume = {38},
    year = {2006}
}

When referred in the text by \textcite{dewach06} prints Dewachter et al. (2006). However:

@article{diebmac06,
    title = {The Macroeconomy and the Yield Curve: A Dynamic Latent Factor Approach},
    year = {2006},
    author = {Francis Diebold and Boragan Aruoba},
    institution = {National Bureau of Economic Research, Inc},
    type = {NBER Working Papers},
    number = {10616},
    url = {https://pdfs.semanticscholar.org/e876/92b94447574a05280cdf2e90ee1e77443a30.pdf}
}  

when cited with the same function \textcite prints: Diebold; Aruoba (2006).

I see no difference between the format of these two .bib entries, leaving only Diebold as an author works fine, adding another (third) author puts et al. after Auroba. I am clueless about this, and since my thesis should look nice, I need to fix this.

Answer 1

If I only put the two entries from the question into a document with style=iso-authoryear I get

Dewachter et al., 2006; Diebold et al., 2006

in the citations. You say you get "Diebold; Aruoba (2006)" and that suggests that the uniquelist feature is involved (cf. Set limit to one author when using "et al." in biblatex). Presumably you have another entry where Diebold is also the first author, but that was not written by Diebold and Aruoba. (I faked such an entry for the example below.)

I personally find "Dewachter et al." for "Dewachter and Lyrio" unnecessary. Traditionally "et al." is seen as a plural abbreviation and should only replace two or more authors in a two-author list it may be slightly longer, but feels nicer, to also give the second author's name properly. I have no idea what your interpretation of ISO 690 has to say about that, but I could not find anything on this for citations in the English ISO 690. For the bibliography it only seems to be acceptable to use "et al." for lists of more than three authors (ISO 690:2010, 5.4.1 & 5.4.2).

I would also suggest to make diebmac06 a @report entry and not an @article. There might be a small problem with that at the moment (see https://github.com/michal-h21/biblatex-iso690/issues/70), but semantically @report is the much better type here. An @article should absolutely have a journal.

---

Finally, to your question.

If you want to see

Diebold a Aruoba (2006)

instead of

Diebold; Aruoba (2006)

you need to tweak finalnamedelim and multinamedelim.

The MWE produces the same results as an unmodified biblatex-iso in the bibliography, but uses comma and "and" in the citations.

\documentclass[czech]{article}
\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}
\usepackage{babel}
\usepackage{csquotes}

\usepackage[style=iso-authoryear, backend=biber]{biblatex}

\DeclareDelimFormat{multinamedelim}{\addcomma\space}
\DeclareDelimFormat{finalnamedelim}{%
  \ifnumgreater{\value{liststop}}{2}{\finalandcomma}{}%
  \addspace\bibstring{and}\space}

\DeclareDelimFormat[bib]{multinamedelim}{\addsemicolon\space}
\DeclareDelimAlias*[bib]{finalnamedelim}{multinamedelim}

\usepackage{filecontents}
\begin{filecontents}{\jobname.bib}
@article{dewach06,
  ISSN      = {00222879, 15384616},
  URL       = {http://www.jstor.org/stable/3839071},
  author    = {Hans Dewachter and Marco Lyrio},
  journal   = {Journal of Money, Credit and Banking},
  number    = {1},
  pages     = {119--140},
  publisher = {[Wiley, Ohio State University Press]},
  title     = {Macro Factors and the Term Structure of Interest Rates},
  volume    = {38},
  year      = {2006}
}
@report{diebmac06,
  title       = {The Macroeconomy and the Yield Curve: A Dynamic Latent Factor Approach},
  year        = {2006},
  author      = {Francis Diebold and Boragan Aruoba},
  institution = {National Bureau of Economic Research, Inc},
  type        = {NBER Working Papers},
  number      = {10616},
  url         = {https://pdfs.semanticscholar.org/e876/92b94447574a05280cdf2e90ee1e77443a30.pdf}
}
@report{diebmac07,
  title       = {The Macroeconomy and the Yield Curve: A Dynamic Latent Factor Approach},
  year        = {2007},
  author      = {Francis Diebold and Aoragan Bruoba},
  institution = {National Bureau of Economic Research, Inc},
  type        = {NBER Working Papers},
  number      = {10616},
  url         = {https://pdfs.semanticscholar.org/e876/92b94447574a05280cdf2e90ee1e77443a30.pdf}
}
\end{filecontents}

\addbibresource{\jobname.bib}

\begin{document}
\cite{dewach06,diebmac06,diebmac07}
\printbibliography
\end{document}

gives

Dewachter et al., 2006; Diebold a Aruoba, 2006; Diebold a Bruoba, 2007

in citations and

DIEBOLD, Francis; ARUOBA, Boragan, 2006. The Macroeconomy and the Yield Curve: A Dynamic Latent Factor Approach. Dostupné také z: https://pdfs.semanticscholar.org/e876/92b94447574a05280cdf2e90ee1e77443a30.pdf. NBER Working Papers. National Bureau of Economic Research, Inc.

in the bibliography.

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If you have reason to believe that the default behaviour of biblatex-iso goes against ISO 690, against the Czech or Slovakian translation of the norm or even only against a common interpretation of the norm, please open an issue at https://github.com/michal-h21/biblatex-iso690/issues. Ideally you would include a full example document (not unlike the one in this answer) and could back up your claims about non-compliance with the norm with citations or exact references to certain clauses of the norm (or your interpretation of the norm).