  The thickness dependence of spin-orbit torque and magnetoresistance in
ferromagnet/heavy-metal bilayers is studied using the first-principles
non-equilibrium Green's function formalism combined with the Anderson disorder
model. A systematic expansion in orthogonal vector spherical harmonics is used
for the angular dependence of the torque. The damping-like torque in Co/Pt and
Co/Au bilayers can be described as a sum of the spin-Hall contribution, which
increases with thickness in agreement with the spin-diffusion model, and a
comparable interfacial contribution. The magnetoconductance in the plane
perpendicular to the current in Co/Pt bilayers is of the order of a conductance
quantum per interfacial atom, exceeding the prediction of the spin-Hall model
by more than an order of magnitude. This suggests that the "spin-Hall
magnetoresistance," similarly to the damping-like torque, has a large
interfacial contribution unrelated to the spin-Hall effect.
