# Use special objects of xy-pic with beamer

When I try to use the general format for labels (cf. xyguide, §2.2) together with beamer overlays, the part that should show up later isn't formatted properly. I guess, beamer doesn't convert the * properly. What can I do? See the code below.

\documentclass{beamer}

\mode<presentation>
{
\usecolortheme{seahorse}
\setbeamercovered{covered}
}

\usepackage{tikz}
\usepackage[all]{xy}

\begin{document}
\begin{frame}
$\xymatrix@=1.5em{ *++[o][F]{C} \only<+->{\ar@/^/[r]^{\alpha\rho}} & \uncover<.->{*++[o][F]{Z}} \only<.->{\ar@/^/[l]^{100\%}} }$
\end{frame}

\end{document}
-

$\xymatrix@=1.5em{ *++[o][F]{C} \only<+->{\ar@/^/[r]^{\alpha\rho}} & *++[o][F]{Z} \only<.->{\ar@/^/[l]^{100\%}} }$