Surface superconductivity and H_c3 in UPt₃

Ginzburg-Landau (GL) theory is used to study surface superconductivity for UPt₃ for various order parameter symmetries (OPS), and H_c3 is found for all principal directions of the surface normal n̂ and the field [1]. Assuming specular reflection, and allowing for reorientation of the antiferromagnetic symmetry breaking field in the models with E_1g, E_2g, E_1u, or E_2u symmetry, the experiments of Keller et al. [2] with n̂ = â can be qualitatively explained for all OPS except possibly A_1u ⊕ B_1u. The implied GL parameters then predict qualitatively different and OPS dependent behavior for n̂ = â* and n̂ = ĉ. Study of H_c3 for these surfaces would give strong clues about the OPS of UPt₃.