GINZBURG-LANDAU THEORY OF THE PHASE-DIAGRAM OF SUPERCONDUCTING UPT3

The phase diagram of superconducting UPt3 is investigated within a Ginzburg-Landau theory that uses a complex two-component vector order parameter. For fields both along the c axis and in the basal plane, the theory allows for a kink in H(c2)(T), but the inner lines may not be true phase boundaries. For basal plane fields, an additional transition is predicted at which a magnetization transverse to the field develops. For otherwise-oriented fields, there is no kink in H(c2). The nature of the order parameter in the various phases is determined.