How to remove the final comma in a list of authors; biblatex with natbib compatibility mode

Question

the MWE will show you the problem I am faced with. I want to remove the comma after the second author so that I obtain: "author1, author2 and author3 (year)". With the settings in the MWE, I obtain: "author1, author2, and author3 (year)".

\documentclass[
    twoside,openright,titlepage,numbers=noenddot,headinclude,
    footinclude=true,cleardoublepage=empty,
    headsepline,
    dottedtoc,
    BCOR=5mm,paper=a4,fontsize=11pt, 
    ngerman,american,
    ]{scrreprt} 


   \PassOptionsToPackage{utf8}{inputenc}
   \usepackage{inputenc}
   \usepackage[american]{babel}

   \PassOptionsToPackage{%
    backend=biber,
    isbn = false,
    doi = false,
    language=auto,
    style=authoryear-comp,
    sorting=nyt,
    maxbibnames=1,
    natbib=true
    }{biblatex}
    \usepackage{biblatex}

    \addbibresource{citation-292640248.bib}

    \usepackage{classicthesis} 

    \begin{document}
        When citing with citet one obtains for example: 
        \citet{Antoniadis.1992}.
    \end{document}

The corresponding bib.-file reads:

@article{Antoniadis.1992,
 author = {Antoniadis, D. and Mantzavinos, D. and Stamatoudis, M.},
 year = {1992},
 month = {03},
 pages = {161-165},
 title = {Effect of chamber volume an diameter on bubble formation at plate 
 orifices},
 volume = {70}
 }

Answer 1

Either your typographic objective (removing the so-called Oxford comma) or parts of your document setup need to adjust.

Since you've (a) chosen american to be the primary language for babel and (b) set the option language=auto for biblatex, you're getting the Oxford comma before the final "and" precisely because using the Oxford comma is, in fact, standard US-English (as well as Canadian-English) formatting practice.

You have (at least) three options:

• Do nothing, i.e., keep your current document setup and get used to the Oxford comma.

• Switch to a variant of English (e.g., british or australian, among others) that doesn't employ the Oxford comma by default. Note that such a switch can have far-reaching and unexpected consequences, in part because hyphenation patterns tend to differ considerably across variants of the English language. (Aside: Isn't it mildly amusing that the Oxford comma is used in the U.S. but not in the U.K.?!)

• If you do need to use the american variant of English as the default language but simply can't stand the look of Oxford commas, insert the instruction

  \DefineBibliographyExtras{american}{\let\finalandcomma=\empty}
  

  after loading biblatex.

For much more information on this topic, see the posting Multiple authors in (classicthesis) Bibliography: removing comma before "and".