How to set the counter of the part in classic-thesis?

Question

I am using classic-thesis and my document structure is:

- Intro
Part I: Background
- chap
...
Intermezzo
- chap
...
- Part II: ...
- chap
...

I created a "Intermezzo" part (for lack of better name) with no number by changing:

\renewcommand{\thepart}{}

and then back to

\renewcommand{\thepart}{\roman{part}}

But I get:

 - Intro
    Part I: Background
    - chap
    ...
    Intermezzo
    - chap
    ...
    - Part III: ...
    - chap
    ...

I have tried to % \@addtoreset{part}{thepart} and

\@addtoreset{part}{thepart}
\setcounter{part}{2}
\setcounter{thepart}{2}

The counter is never changed. Besides, in the part page it says "Part" without the number.

How can set the \thepart counter and say that if its is zero (or something else) it should not print "Part" (\partname) nor \thepart?

Answer 1

With the KOMA-Script use \addpart{Intermezzo} to add a no-numbered part but listed in the table of contents. \addchap{Intro} takes care of chapters.

\documentclass{scrbook}
\usepackage{classicthesis}
\begin{document}
\tableofcontents
\addchap{Intro}
\part{Background}
\chapter{One}
\addpart{Intermezzo} % part without number, listed in TOC
\chapter{Two}
\part{Second}
\chapter{Three}
\end{document}

With the standard book class use \part*{...} to get a no-number part. As probably you will want to include it in the table of contents add \addtocontents{TOC}{part}{Intermezzo}

But

The classicthesis package uses titlesec to handle its title formatting. titlesec strongly discourages the use of starred versions of things.

See https://tex.stackexchange.com/a/16525/161015 for a better way.

\documentclass[12pt, twoside]{book}
\usepackage[parts]{classicthesis}
\begin{document}
\tableofcontents
\chapter*{Intro}
\addcontentsline{toc}{chapter}{Intro}   % include in the TOC
\part{Background}
\chapter{One}
\part*{Intermezzo}
\addcontentsline{toc}{part}{Intermezzo} % include in the TOC
\chapter{Two}
\part{Second}
\chapter{Three}
\end{document}