Magnetotransport in the heavy-fermion system ${\mathrm{YbNi}}_2{\mathrm{B}}_2\mathrm{C}$

We have measured the high field transverse magnetoresistance and magnetization on single crystalline samples of ${\mathrm{YbNi}}_2{\mathrm{B}}_2\mathrm{C}$ with the applied magnetic field both parallel and perpendicular to the c axis of the tetragonal crystal structure. At high temperatures, the magnetoresistance is negative with a magnitude that increases as the temperature is lowered. A scaling analysis of the data for $\mathbf{H}\perp \mathbf{c}$ finds a characteristic energy that is ∼20 K at low temperatures, which is a factor of 2 larger than the Kondo temperature determined from thermodynamic measurements, and it increases linearly with the temperature. Even though the magnetoresistance for $\mathbf{H}\parallel \mathbf{c}$ is also negative, the data do not scale. At low temperatures, the magnetoresistance is very anisotropic. In the Fermi-liquid regime below ∼1.6 K, the resistivity has a temperature-independent contribution due to ligand and/or Kondo-hole disorder and a term from electron-electron scattering that goes like $T^2.$ For $\mathbf{H}\perp \mathbf{c},$ the residual resistivity and the $T^2$ coefficient are field dependent. Both the high- and low-temperature data are compared to various theoretical calculations.