IDENTIFICATION OF ODD-PARITY SUPERCONDUCTIVITY IN UPT3 FROM PARAMAGNETIC EFFECTS ON THE UPPER CRITICAL-FIELD

We present a theoretical explanation of the unusual temperature-dependent anisotropy of H(c2) reported by Shivaram et al. for single crystals of UPt3, which we argue provides strong support for unconventional odd-parity pairing. We show that the observed low-temperature crossover in the anisotropy ratio, H(c)2 perpendicular-to/H(c)2, parallel-to can be explained by paramagnetic limiting for H parallel to the sixfold axis within BCS pairing theory if the order parameter has odd parity and there is strong spin-orbit coupling of the pair spin to the crystal axes.