  We studied the drift of electron spins under an applied DC electric field in
single layer graphene spin valves in a field effect transport geometry at room
temperature. In the metallic conduction regime ($n \simeq 3.5 \times 10^{16}$
m$^{-2}$), for DC fields of about $\pm$70 kV/m applied between the spin
injector and spin detector, the spin valve signals are increased/decreased,
depending on the direction of the DC field and the carrier type, by as much as
$\pm$50%. Sign reversal of the drift effect is observed when switching from
hole to electron conduction. In the vicinity of the Dirac neutrality point the
drift effect is strongly suppressed. The experiments are in quantitative
agreement with a drift-diffusion model of spin transport.
