Anisotropy of the upper critical field in the magnetic heavy-fermion superconductor URu2Si2

Abstract
Measurements have been performed of the upper critical field Hc2 anisotropy in the magnetic heavy‐fermion superconductor URu2Si2. The dHc2/dT value is constant within 5% when H is rotated in the basal plane, whereas ‖dHc2/dT‖ decreases by about 35% for H rotated by 20°–30° out of the basal plane. Contrary to CeCu2Si2 the Hc2 anisotropy in URu2Si2 is enhanced as temperature decreases below Tc. This disparity can be attributed to the different strengths of paramagnetic and spin‐orbit effects responsible for the suppression of superconductivity by a magnetic field in CeCu2Si2 and URu2Si2.