Characterization of the superconducting transition in single-crystal URu sub(2)Si sub(2)

To investigate the nature of the superconducting transition in URu sub(2)Si sub(2) we have made careful studies of the specific heat on oriented samples cut from a high-quality single crystal. Our high-resolution a.c.-specific-heat experiments establish the existence of only one sharp superconducting transition. Measurements in applied fields of up to 5 Tesla show that fields along both the a and c axes induce no splitting of the transition. From these C sub(p)(H) results the upper critical field can be obtained, elucidating for the first time the bulk behaviour of H sub(c2)(T).