\footcite and \footcitetext produce empty citation in beamer [closed]

I'm using biblatex with bibtex in the beamer document class. In a very weird way the \footcite produces a rather empty citation "2." In the example, whereas \footcitefull gives a very nice citation.

My problem now is that I would like to place a citation within a column and/or block environment, where according to other posts I would have to use \footnotemark and \footcitetext, which would simply write "3." in the footer.

For image, see:

My question would be:

1. Is there an error in my TeX or
2. is there an equivalent to \footcitefull in \footcitetext?

documentclass[8pt]{beamer}
\usepackage[utf8]{inputenc}
%\usepackage[ngerman]{babel}
\usepackage{hyperref}
\usepackage{graphicx}
%\usepackage[pdftex]{color}
%\usepackage{colortbl}
%\usepackage{listings}
\usepackage{xcolor}
\usepackage[lf]{venturis}
\usepackage{amsmath}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{subcaption}
%\usepackage{multirow}
\usepackage[version=3]{mhchem}
%\usepackage{longtable}
\usepackage{pgf}
\usepackage{tikz}
\usepackage[citetracker=true,sorting=none,backend=bibtex,autocite=footnote]{biblatex}
\bibliography{../literature.bib}
\frame{
\frametitle{Introduction -- Electron Magnetic Chiral Dichroism}

\begin{itemize}
\item Discovered due to analogies between polarization and scattering vector in theoretical treatment.\footfullcite{emcd_nature}
\item Recent research focused on: signal enhancement, electron vortex'' beams.\footcite{emcd_theory}
\end{itemize}

\begin{block}{Intrinsic Setup}
\begin{columns}[m]
\column{.4\textwidth}
\begin{figure}[h]
\includegraphics[width=.8\columnwidth]{images/apertures_0.pdf}
\caption{Schematic}
\end{figure}

\column{.4\textwidth}
\begin{itemize}
\item The usual'' setup.
\item Phase shift of $\pi/2$ of one Bragg beam due to dynamical diffraction effects.
\item Dependent on sample thickness, orientation and crystal quality.
\item Other setup to overcome dynamical diffraction effects?
\item \textbf{Candidates:}
\begin{itemize}
\item Electron vortex beams (fork aperture, stigmator).
\item Twin aperture with electrostatic phase plates.
\end{itemize}
\end{itemize}
\end{columns}
\end{block}


}

-

closed as too localized by lockstep, Guido, Thorsten, Claudio Fiandrino, KurtDec 10 '12 at 18:04

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–  Claudio Fiandrino Dec 10 '12 at 15:21
The "rather empty" footnote citations correspond to the citation label. Since you use the default numeric style, the label is simply the labelnumber. Why not try using a style with more verbose labels, like authortitle or verbose? –  Audrey Dec 10 '12 at 15:51
Actually, I'm using the style phys as I want to have more nicely formated citations. But I have to admit, it is working with style authortitle. Any idea why it's not working with phys? –  Andi Dec 12 '12 at 7:52
Because biblatex-phys is also a numeric style. –  Audrey Dec 15 '12 at 5:18