We present a theoretical study of the orbital magnetoresistance in a uniaxial anisotropic metal within the relaxation-time approximation. The appearance of a new dimensionless scale, $\delta {=4t}_{\perp }/{\epsilon }_F,$ allows the possibility of a new region at intermediate fields where the magnetoresistance is linear in applied magnetic field for currents flowing along the uniaxial direction. (Here, $t_{\perp }$ characterizes the bandwidth along the uniaxial direction.) In the limit of large anisotropy (small δ), corresponding to a quasi-two-dimensional metal made up of weakly coupled layers, we obtain an analytic expression for the magnetoresistance valid for all magnetic fields. We test our analytic results numerically and we compare our expressions with the c-axis magnetoresistance of ${\mathrm{Sr}}_2{\mathrm{RuO}}_4.$

• Received 15 February 2000

DOI:https://doi.org/10.1103/PhysRevB.62.10779