  Germanium-based alloys hold great promise for future spintronics
applications, due to their potential for integration with conventional Si-based
electronics. Mn5Ge3 exhibits strong ferromagnetism up to the Curie temperature
Tc~295K. We use Point Contact Andreev Reflection (PCAR) spectroscopy to measure
the spin polarization of Mn5Ge3 epilayers grown by solid phase epitaxy on
Ge(111). In addition, we calculate the spin polarization of bulk Mn5Ge3 in the
diffusive and ballistic regimes using density-functional theory. The measured
spin polarization, Pc=43+/-5% is compared to our theoretical estimates,
PDFT=10+/-5% and 35+/-5% in the ballistic and diffusive limits respectively.
