The error has nothing to do with csquotes -- biblatex does not allow nested citations. In your case, I'd use \foreignblockquote (without the "c") and the \cites "Qualified citation list" command (see section 3.7.3 of the biblatex manual). (Note that because I use \cites' optional argument, I have to wrap the command into additional braces in the optional argument of \foreignblockquote.)
\documentclass{article}
\usepackage[ngerman,english]{babel}
\usepackage{csquotes}
\usepackage[style=authoryear]{biblatex}
\SetCiteCommand{\autocite}
\usepackage{blindtext}
\usepackage{filecontents}
\begin{filecontents}{\jobname.bib}
@misc{A01,
author = {Author, A.},
year = {2001},
title = {Alpha},
}
@misc{B02,
author = {Buthor, B.},
year = {2002},
title = {Bravo},
}
\end{filecontents}
\addbibresource{\jobname.bib}
\begin{document}
\blindtext
\foreignblockcquote{ngerman}{A01}{\blindtext}
\foreignblockquote{ngerman}[{\cites{A01}[see also][]{B02}}]{\blindtext}
\printbibliography
\end{document}
Second solution
Edited again, so most multicite commands work.
Edited so \footcite now works.
A reasonably effective solution that preserves many of biblatex's featuers is provided by adjusting the way the year gets printed in citations. This can be done by redifining the commands associated to cite:year and cite:extrayear. This has the advantage of preserving the ibidem feature.
The code below includes a sample bibliography and then the main file with the redefined citation code.
\begin{filecontents}{test.bib}
@Article{Test,
author = {Author, A. N.},
title = {Article title},
year = 2005,
pages = {10-20},
journal = {Jour.},
vol = {100}
}
@Article{Test2,
author = {Author, A. N.},
title = {Second article},
year = 2005,
pages = {10-20},
journal = {Jour.},
vol = {100}
}
@Article{Test3,
author = {Author, A. B.},
title = {Third article},
year = 2005,
pages = {10-20},
journal = {Jour.},
vol = {100}
}
@Article{Test4,
author = {Author, A. N.},
title = {Fourth article},
year = 2007,
pages = {10-20},
journal = {Jour.},
vol = {100}
}
\end{filecontents}
\documentclass{article}
\usepackage[style=authoryear-icomp,autocite=plain]{biblatex}
\addbibresource{test.bib}
\renewbibmacro*{cite:labelyear+extrayear}{%
\iffieldundef{labelyear}
{}
{\iftoggle{blx@footnote}
{\printtext[bibhyperref]{%
\printfield{labelyear}%
\printfield{extrayear}}}
{\footnote{\printtext[bibhyperref]{%
\printfield{labelyear}%
\printfield{extrayear}}}}}}
\renewbibmacro*{cite:extrayear}{%
\iffieldundef{extrayear}
{}
{\iftoggle{blx@footnote}
{\printtext[bibhyperref]{\printfield{extrayear}}}%
{\footnote{\printtext[bibhyperref]{%
\printfield{labelyear}%
\printfield{extrayear}}}}}}
\renewcommand{\compcitedelim}{\space}
\begin{document}
\thispagestyle{empty}
\autocite{Test} and
\autocite[page 3]{Test}.
Some text \parencite{Test2}.
Here is a footnote citation\footcite{Test}.
\autocite{Test,Test4,Test3}.
\printbibliography
\end{document}
As the above shows this works with \autocite, \parencite and accepts their optional arguments. In this style \autocite is the same as \cite.
I haven't demonstrated \textcite, though its ouptut may be useful sometimes; \footcite has also been set up to work, thanks to biblatex's blx@footnote toggle that detects whether we are in a footnote or not.
The code also takes care of most multiple citations \cite{ref1,ref2}. However, there is a spurious comma, if ref1 and ref2 are two publications from the same author in the same year. Fixing that requires, more substanitial rewriting of the citation style file: each of the commands \cite, \textcite, etc. in author-icomp.cbx contains an explicit comma via \setunit{\addcomma}, that needs to be deleted.
Original solution
Here is a repost of the original solution, as this apparently helps the OP best. It simply defines a newcommand \citepfy (plain-foot-year) that calls \citeauthor followed by a modified \footcite command that produces only the year. It does not accept any of the optional arguments cite commands in biblatex usually do.
\begin{filecontents}{b.bib}
@Article{Test,
author = {Author, A. N.},
title = {Article title},
year = 2005,
pages = {10-20},
journal = {Jour.},
vol = {100}
}
\end{filecontents}
\documentclass{article}
\usepackage[style=authoryear-icomp]{biblatex}
\addbibresource{b.bib}
\newcommand{\citepfy}[1]{\citeauthor{#1}\footyearcite{#1}}
\DeclareCiteCommand{\footyearcite}[\mkbibfootnote]
{\usebibmacro{cite:init}%
\usebibmacro{prenote}}
{\usebibmacro{citeindex}%
\usebibmacro{citeyear}}
{}
{\usebibmacro{cite:postnote}}
\begin{document}
\citepfy{Test}
\printbibliography
\end{document}
Best Answer
you may want to to try
\footfullciteinstead of\footcite.[From Audrey] Adding the line:
in the preamble and the using
\footlessfullcite{<entry key>}results in a nice footnote citation.