Nearly isotropic d-wave pairing in UPt3

The available phase diagram of UPt3 in H-T-P coordinates imposes strong restrictions on all theories which are going to explain it. We present a self-consistent solution of this problem. In our picture UPt3 is a d-wave nearly isotropic superconductor with small splitting of critical temperature according to the irreducible representations of a D6h group. Two of these representations A1g and E1g are responsible for the phase transitions in UPt3. The order of high- and low-temperature representations reverses under pressure. This scenario explains all the peculiarities of the UPt3 phase diagram such as the existence of a tetracritical point in the H-T plane, a kink in Hc2(T) for different orientations of magnetic field, the behavior of superconducting phases under pressure and others. ((orig.))