Replace 'and' with ampersand in bibliography and parenthetical citations using BibLaTeX

Question

By default, author-year style in BibLaTeX uses the word 'and' before the last author. I would like to retain this for in-text citations, but would like to replace 'and' with an ampersand (&) in the bibliography and in parenthetical citations.

For example, I would like the following:

In-text citation: Smith and John (2013)
Parenthetical citation: (Smith & John, 2013)
Bibliography: Smith, A.B. & John, C.D. (2013)...

How can I do this? I found another answer that specified how to turn all instances of 'and' to ampersand, but I haven't been able to find out how to change only the bibliography and parenthetical citations to ampersand (not the in-text citations):

Use ampersand & in citations and bibliography in biblatex

Answer 1

Using the code in the linked answer, this is what you can do.

To replace and with & in the bibliography you can simply insert that code inside \AtBeginBibliography:

\AtBeginBibliography{%
  \renewcommand*{\finalnamedelim}{%
    \ifnumgreater{\value{liststop}}{2}{\finalandcomma}{}%
    \addspace\&\space}%
}

The second request is a bit more complicated, in my opinion. Supposing you are using \parencite for parenthetical citations, you can redefine that command in this way:

\let\origparencite\parencite
\renewrobustcmd{\parencite}{%
  \AtNextCite{%
  \renewcommand*{\finalnamedelim}{%
    \ifnumgreater{\value{liststop}}{2}{\finalandcomma}{}%
    \addspace\&\space}%
  }%
  \origparencite%
}

\AtNextCite ensures that and is changed to & only for the current citation command.

MWE (borrowed from the linked answer):

\documentclass{article}

\usepackage[style=authoryear]{biblatex}

\AtBeginBibliography{%
  \renewcommand*{\finalnamedelim}{%
    \ifnumgreater{\value{liststop}}{2}{\finalandcomma}{}%
    \addspace\&\space}%
}

\let\origparencite\parencite
\renewrobustcmd{\parencite}{%
  \AtNextCite{%
  \renewcommand*{\finalnamedelim}{%
    \ifnumgreater{\value{liststop}}{2}{\finalandcomma}{}%
    \addspace\&\space}%
  }%
  \origparencite%
}

\usepackage{filecontents}

\begin{filecontents}{\jobname.bib}
@misc{A01,
  author = {Author, A. and Buthor, B. and Cuthor, C.},
  year = {2001},
  title = {Alpha},
}
\end{filecontents}

\addbibresource{\jobname.bib}

\begin{document}

Normal citation: \cite{A01}.

Parenthetical citation: \parencite{A01}.

Normal citation: \cite{A01}.

\printbibliography

\end{document} 

Output:

Answer 2

With a current version of biblatex (tested with v3.16 [2020-12-31], but the basics were already present in v3.4 [2016-05-10]) you can use the context-sensitive delimiter interface.

To change the "and" to "&" in \parencite and the bibliography use the following

\documentclass[british]{article}
\usepackage[T1]{fontenc}
\usepackage{babel}
\usepackage{csquotes}

\usepackage[style=authoryear]{biblatex}

\DeclareDelimFormat[bib,parencite]{finalnamedelim}{%
  \ifnumgreater{\value{liststop}}{2}{\finalandcomma}{}%
  \addspace\&\space}

\addbibresource{biblatex-examples.bib}

\begin{document}
Normal citation: \cite{sigfridsson}.

Parenthetical citation: \parencite{sigfridsson}.

Textual citation: \textcite{sigfridsson}.

\printbibliography
\end{document}

---

I should note that the different separator between authors depending on the context is a feature of APA style. If you are looking for full APA style, you may want to look into biblatex-apa instead.

\documentclass[american]{article}
\usepackage[T1]{fontenc}
\usepackage{babel}
\usepackage{csquotes}

\usepackage[style=apa]{biblatex}

\addbibresource{biblatex-examples.bib}

\begin{document}
Normal citation: \cite{sigfridsson}.

Parenthetical citation: \parencite{sigfridsson}.

Textual citation: \textcite{sigfridsson}.

\printbibliography
\end{document}