UPt 3 at very low temperatures: Specific heat in high magnetic fields

Abstract

Abstract In order to determine the spectrum of low energy excitations in the heavy fermion system UPt 3 in both its normal and superconducting states we have measured the specific heat of a single crystal down to temperatures below 15 mK and in magnetic fields up to 7 T. The specific heat shows a surprising upturn in c/T below 50 mK which prevails in magnetic fields far above H c2 (after subtraction of the nuclear specific heat of 195 Pt). We also present data on the low field (10 Oe) d.c. susceptibility down to 1.2 mK which varies as T 2 in the s.c. state. This reflects the T-dependence of the London penetration depth and also proves that superconductivity persists down to this temperature.