Odd parity and line nodes in heavy-fermion superconductors

Group theory arguments have demonstrated that a general odd-parity order parameter cannot have line nodes in the presence of spin-orbit coupling. In this paper, it is shown that these arguments do not hold on the kz={π}/c zone face of a hexagonal close-packed lattice. In particular, three of the six odd-parity representations vanish identically on this face. This has potential relevance to the heavy fermion superconductor UPt₃.