Anisotropic resistivity and normal-state magnetoresistance of RNi2B2C (R = Y, Lu, Er, Ho)

Results of direct measurements of the in-plane and c-axis resistivity of single crystals of RNi2B2C (R = Y, Lu, Er, Ho) are presented. Despite the layered crystal structure, the resistivity of these materials is shown to be fundamentally isotropic. Small deviations from this isotropic behavior are observed below approximately 150 K for the compounds containing magnetic rare-earth ions (Er and Ho), probably due to crystal-electric-field effects. In addition, it is shown that the in-plane normal-state resistivity of ErNi2B2C and HoNi2B2C follows the same temperature dependence as that of the nonmagnetic materials (YNi2B2C and LuNi2B2C), but with an additional temperature-independent contribution (i.e., the resistivity of the magnetic compounds is shifted upwards by a few mu Omega cm). The observation of a striking negative longitudinal magnetoresistance for HoNi2B2C, which is not observed for LuNi2B2C, indicates that this difference is due to spin-disorder scattering. [S0163-1829(97)00542-0].