Anisotropic gap distortion due to superflow and the depairing critical current in superfluid 3He-B

The specific heats of UAs and the isostructural nonmagnetic homolog ThAs have been measured in the temperature range 5–300 K. While the latter compound displays a regular smooth curve C _p (T), UAs shows two sharp anomalies. The first anomaly, around 64 K, may be ascribed to the magnetic transition from type IA to type I antiferromagnetic structure; the second anomaly, at 122.8 K, corresponds to the Néel temperature. An analysis of the experimental curve C _p (T) for UAs has been carried out by several different methods to get the magnetic contribution to the specific heat with the best possible accuracy. The resulting magnetic entropy depends on the method and its maximum value at 250 K is 0.8 R ln 4, assuming a high-temperature value of the electronic heat capacity coefficient – 33 mJ/K² mole. No anomaly at 41 K was observed whatever thermal treatment was used to prepare the UAs samples.