  Using high-quality Fe$_{3}$Si/$n^{+}$-Ge Schottky-tunnel-barrier contacts, we
study spin accumulation in an $n$-type germanium ($n$-Ge) channel. In the
three- or two-terminal voltage measurements with low bias current conditions at
50 K, Hanle-effect signals are clearly detected only at a forward-biased
contact. These are reliable evidence for electrical detection of the spin
accumulation created in the $n$-Ge channel. The estimated spin lifetime in
$n$-Ge at 50 K is one order of magnitude shorter than those in $n$-Si reported
recently. The magnitude of the spin signals cannot be explained by the commonly
used spin diffusion model. We discuss a possible origin of the difference
between experimental data and theoretical values.
