Magnetotransport of CeRhIn₅

We report measurements of the temperature-dependent anisotropic resistivity and in-plane magnetoresistance on single crystals of the tetragonal heavy-fermion antiferromagnet (T_N = 3.8 K) CeRhIn₅. The measurements are reported in the temperature range 1.4-300 K and in magnetic fields to 18 T. The resistivity is moderately anisotropic, with a room-temperature c-axis to in-plane resistivity ρ_c/ρ_a (300 K) = 1.7. ρ(T) measurements on the nonmagnetic analog LaRhIn₅ indicate that the anisotropy in the CeRhIn₅ resistivity stems predominantly from anisotropy in Kondo-derived magnetic scattering. In the magnetically ordered regime, an applied field H reduces T_N only slightly due to the small ordered moment (0.37/μ_B) and magnetic anisotropy. The magnetoresistance (MR) below TN is positive and shows little sign of saturating in fields to 18 T. In the paramagnetic state, a positive MR is present below 7.5 K, while a high-field negative contribution is evident at higher temperatures. The positive contribution decreases in magnitude with increasing temperature. Above 40 K the positive contribution is no longer observable, and the MR is negative. The low-T positive MR results from interactions with the Kondo-coherent state, while the high-T negative MR stems from single-impurity effects. In general, these results indicate that CeRhIn₅ exhibits a modest degree of transport anisotropy not atypical among heavy-fermion compounds.