  We studied the magnetoresistance of normal metal (NM)/ferromagnet (FM)
bilayers in the linear and nonlinear (current-dependent) regimes and compared
it with the amplitude of the spin-orbit torques and thermally induced electric
fields. Our experiments reveal that the magnetoresistance of the heavy NM/Co
bilayers (NM = Ta, W, Pt) is phenomenologically similar to the spin Hall
magnetoresistance (SMR) of YIG/Pt, but has a much larger anisotropy, of the
order of 0.5%, which increases with the atomic number of the NM. This SMR-like
behavior is absent in light NM/Co bilayers (NM = Ti, Cu), which present the
standard AMR expected of polycrystalline FM layers. In the Ta, W, Pt/Co
bilayers we find an additional magnetoresistance, directly proportional to the
current and to the transverse component of the magnetization. This so-called
unidirectional SMR, of the order of 0.005%, is largest in W and correlates with
the amplitude of the antidamping spin-orbit torque. The unidirectional SMR is
below the accuracy of our measurements in YIG/Pt.
