  A unique spin depolarization mechanism, induced by the presence of g-factor
anisotropy and intervalley scattering, is revealed by spin transport
measurements on long-distance germanium devices in a longitudinal magnetic
field. The confluence of electron-phonon scattering (leading to Elliott-Yafet
spin flips) and this previously unobserved physics enables the extraction of
spin lifetime solely from spin-valve measurements, without spin precession, and
in a regime of substantial electric-field-generated carrier heating. We find
spin lifetimes in Ge up to several hundreds of ns at low temperature, far
beyond any other available experimental results.
