Topologically stable gapless phases in nonsymmorphic superconductors
  We study topological stability of nodes in nonsymmorphic superconductors (SCs). In particular, we demonstrate that line nodes in nonsymmirphic odd-parity SCs are protected by the interplay between topology and nonsymmorphic symmetry. As an example, it is shown that the $E_{2u}$-superconducting state of UPt$_3$ hosts the topologically stable line node at the Brillouin zone face. Our theory indicates that the existence of spin-orbit coupling is essential for protecting such a line node, complementing the Norman's group theory argument. Developing the topological arguments, we also argue generalization to point nodes and to other symmetry cases beyond the group theory arguments. 
Shingo Kobayashi, Youichi Yanase, and Masatoshi Sato
cond-mat.supr-con cond-mat.str-el