THERMAL-CONDUCTIVITY ANISOTROPY IN SUPERCONDUCTING UPT3

Recent thermal conductivity measurements on UPt3 single crystals by Lu ssier et al. indicate the existence of a strong b-c anisotropy in the superconducting state. We calculate the thermal conductivity in variou s unconventional candidate states appropriate for the UPt3 ''B phase'' and compare with experiment, specifically the E(2u) and E(1g) (1,i) s tates predicted in some Ginzburg-Landau analyses of the phase diagram. For the simplest realizations of these states over spherical or ellip soidal Fermi surfaces, the normalized E(2u) conductivity is found, sur prisingly, to be completely isotropic. We discuss the effects of inela stic scattering and realistic Fermi surface anisotropy, and deduce con straints on the symmetry class of the UPt3 ground state.