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 ${\mathit{k}}_{\mathit{z}}$=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 ${\mathrm{UPt}}_3$.

• Received 15 June 1995

DOI:https://doi.org/10.1103/PhysRevB.52.15093