voce não menciona a classe e os packages...
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\documentclass{article}
\usepackage[portuges]{babel}
\usepackage[style=authoryear,maxnames=2]{biblatex}
\usepackage{filecontents}
\begin{filecontents}{\jobname.bib}
@misc{Aut10a,
author = {Author, A.},
year = {2010},
title = {And now for something completely different},
}
@misc{Aut10b,
author = {Author, A. and Buthor, B.},
year = {2010},
title = {And now for something completely different},
}
@misc{Aut10c,
author = {Author, A. and Buthor, B. and Cuthor, C.},
year = {2010},
title = {And now for something completely different},
}
\end{filecontents}
\bibliography{\jobname}
\begin{document}
\parencite{Aut10a}
\parencite{Aut10b}
\parencite{Aut10c}
% Name cap also in bibliography
\printbibliography
% No name cap in bibliography
\printbibliography[maxnames=99]
\end{document}
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