POSSIBLE PHASE-DIAGRAMS OF SUPERCONDUCTING UPT3

We enumerate and discuss several possibilities for the split transition in UPt3 and the phase diagrams that result. We find that the splitting may be due to weak basal-plane spin-orbit coupling or a near degeneracy of E1 and A1 representations of the hexagonal group. A further possibility is that only the E1 representation is involved and is split by the coupling to antiferromagnetism, as suggested recently. However, as distinct from the previous results, we found that this coupling could lead to a superconducting glass phase if the antiferromagnetic domain size is small, as is observed. The implications of these ideas for the Hc2 curves are discussed, particularly the questions of the presence of the kink in the Hc2 curves and the isotropy of Hc2 in the basal plane. © 1990 The American Physical Society.