  The recent experimental discovery of three-dimensional (3D) materials hosting
a strong Rashba spin-orbit coupling calls for the theoretical investigation of
their transport properties. Here we study the zero temperature dc conductivity
of a 3D Rashba metal in the presence of static diluted impurities. We show
that, at variance with the two-dimensional case, in 3D systems spin-orbit
coupling affects dc charge transport in all density regimes. We find in
particular that the effect of spin-orbit interaction strongly depends on the
direction of the current, and we show that this yields strongly anisotropic
transport characteristics. In the dominant spin-orbit coupling regime where
only the lowest band is occupied, the SO-induced conductivity anisotropy is
governed entirely by the anomalous component of the renormalized current. We
propose that measurements of the conductivity anisotropy in bulk Rashba metals
may give a direct experimental assessment of the spin-orbit strength.
