Anisotropic inelastic scattering and its interplay with superconductivity in URu₂ Si₂

In contrast to almost all anisotropic superconductors, the upper critical field of URu₂ Si₂ is larger when the field is oriented along the less conducting direction. We present a study of resistivity and Seebeck coefficient extended down to sub-Kelvin temperature range uncovering a singular case of anisotropy. When the current is injected along the c axis URu₂ Si₂ behaves as a low-density Fermi liquid. When it flows along the a axis, even in presence of a large field, resistivity remains T-linear down to Tc and the Seebeck coefficient undergoes a sign change at very low temperatures. We conclude that the characteristic energy scale is anisotropic and vanishingly small in the basal plane.