! LaTeX Error: Command \c@author already defined

Question

I am close to loose my contenance: my preamble:

    \documentclass[twocolumn]{bmcart}% uncomment this for twocolumn layout and comment line below
    %%\documentclass{bmcart}

    %%% Load packages
    \usepackage{amsthm,amsmath}
    \usepackage{graphicx}
    %\usepackage[bmc]{bmc-mathphys}
    \usepackage{caption}
    \usepackage{float}
    \usepackage[latin, german, english]{babel}
    \RequirePackage{hyperref}
    \usepackage[utf8]{inputenc} %unicode support
    %\usepackage[applemac]{inputenc} %applemac support if unicode package fails
    %\usepackage[latin1]{inputenc} %UNIX support if unicode package fails
    \usepackage{dcolumn} %important for tables in the paper!!!)
    \usepackage{url}
    \usepackage{ifthen}
    \usepackage{multicol}
    \usepackage{etoolbox}
     \usepackage{logreq}
    \usepackage{dcolumn} %for package mtable gotoLatex
    \usepackage{booktabs} %for package mtable
    \usepackage{csquotes}
    \bibliographystyle{bmc-mathphys}    % Style BST file
    \usepackage[
    backend=biber,
    %style=authoryear,
    %style=numeric,
    citestyle=numeric,
    bibstyle=numeric,
    url=false,
    doi=false,
    isbn=false, 
    eprint=false, 
    firstinits=true, %adds only initials in bibliography
    terseinits=true, % Removes period after first name intial 
    %dashed=false,
    block=none, %space
    backref=false,
    backrefstyle=three+,
    maxbibnames=99,
    maxcitenames=2,
    hyperref=true,
    sorting=none,
    natbib=true
    ]{biblatex}

    \DeclareNameAlias{sortname}{last-first} % Lists all authors with last name first
    %\setlength{\bibitemsep}{1em}
    %\setlength{\bibhang}{2em}

        %\AtEveryBibitem{\clearfield{note}} %clears note 

    %   or use Biber settings to eliminate notes and language fildes
    \DeclareSourcemap{
      \maps[datatype=bibtex, overwrite]{
       \map{
        \step[fieldset=language, null]
         \step[fieldset=notes, null]
          }
        }
      }

        \addbibresource{Rad.bib}        

    \usepackage[hyphenbreaks, anythingbreaks]{breakurl}

    \usepackage{bm} %for bold math added 10.07.2015
    \graphicspath{{Images/}}

\begin{document}
One of the precariously researched areas for example answers to how temporal aspects can influence the economic or clinical result dimension \citep{de_groot_admission_2012}. There is some evidence on how admission days influence outcome (e.g. mortality) or also other dimensions (\citep{concha_variations_2014} \citep{dismuke_has_1999} )

\clearpage
\printbibliography[heading=bibintoc]
\end{document}

@article{dismuke_has_1999,
    Author = {Dismuke, Clara E. and Sena, Vania},
    Date = {1999-06-01},
    Date-Modified = {2015-12-14 15:55:00 +0000},
    Doi = {10.1023/A:1019027509833},
    File = {},
    Issn = {1386-9620, 1572-9389},
    Journaltitle = {Health Care Management Science},
    Keywords = {},
    Langid = {english},
    Note = {00072},
    Number = {2},
    Pages = {107--116},
    Shortjournal = {Health Care Management Science},
    Shorttitle = {TEST2},
    Url = {http://link.springer.com.ezproxy.unilu.ch/article/10.1023/A%3A1019027509833},
    Urldate = {2014-05-04},
    Volume = {2},
    Bdsk-Url-1 = {http://link.springer.com.ezproxy.unilu.ch/article/10.1023/A%3A1019027509833},
    Bdsk-Url-2 = {http://dx.doi.org/10.1023/A:1019027509833}}

@article{concha_variations_2014,
    Abstract = {},
    Author = {Concha, Oscar Perez and Gallego, Blanca and Hillman, Ken and Delaney, Geoff P. and Coiera, Enrico},
    Date = {2014-03-01},
    Doi = {10.1136/bmjqs-2013-002218},
    File = {},
    Issn = {, 2044-5423},
    Journaltitle = {{BMJ} Quality \& Safety},
    Keywords = {Health services research, Patient Safety, Quality Measurement},
    Langid = {english},
    Note = {00005 {PMID}: 24163392},
    Number = {3},
    Pages = {215--222},
    Shortjournal = {{BMJ} Qual Saf},
    Shorttitle = {TEST},
    Url = {http://qualitysafety.bmj.com/content/23/3/215},
    Urldate = {2014-07-09},
    Volume = {23},
    Bdsk-Url-1 = {http://qualitysafety.bmj.com/content/23/3/215},
    Bdsk-Url-2 = {http://dx.doi.org/10.1136/bmjqs-2013-002218}}

Texstudio generates:

! LaTeX Error: Command \c@author already defined. Or name \end... illegal, see p.192 of the manual.

See the LaTeX manual or LaTeX Companion for explanation. Type H for immediate help. ...

TexShop: generates document despite the error

How can I avoid the generation of author twice or figure out which package to avoid. TXS a lot!

Answer 1

The class bmcart as found on github doesn't seem to be perfectly compatible with biblatex (there are some etoolbox complaints as well).

In particular, it defines a counter \c@author which is later also defined by biblatex. Those two counters have completely different purposes, so it is not a matter of letting one package use the definition of the other.

We can however simply overwrite the class definition (hoping that this doesn't cause problems down the road) and let biblatex do its thing.

\makeatletter
\let\c@author\relax
\makeatother

The following MWE will happily compile with biblatex

\documentclass[british]{bmcart}
\usepackage[utf8]{inputenc}
\usepackage{babel}
\makeatletter
\let\c@author\relax
\makeatother
\usepackage[backend=biber, style=numeric]{biblatex}

\addbibresource{biblatex-examples.bib}        

\begin{document}
\cite{sigfridsson}
\printbibliography
\end{document}

---

Since the class seems to have its own bibliography package (github link) and a BibTeX styles file (github link) that is probably what you should use when submitting to the journal and not biblatex (knowing the issues that might arise when trying to do so).