  The anomalous Nernst effect of thin bilayers comprising a thin normal metal
film and a ferromagnetic Mn$_5$Ge$_3$C$_{0.8}$ film has been investigated.
Epitaxial c-axis grown Mn$_5$Ge$_3$C$_{0.8}$ films have been obtained by e-beam
evaporation as well as by magnetron sputtering on Ge(111) substrates. The size
of the anomalous Nernst coefficient is independent of the growth method. Pt,
Ta, and Pt/Cu bilayers have been used as voltage leads on top of the
ferromagnetic film. We show that the interface between the normal metal
electrode and the ferromagnetic film contributes significantly to the anomalous
Nernst voltage which is suprisingly independent of the choice of the metal. The
interface-induced enhancement of the anomalous Nernst effect is verified for
samples with varying Mn content or undergoing an additional annealing step. The
results suggest that the interface quality has a strong impact on the size of
the anomalous Nernst effect.
