  In noncentrosymmetric metals, the spin degeneracy of the electronic bands is
lifted by spin-orbit coupling. We consider general symmetry properties of the
pairing function Delta(k) in noncentrosymmetric superconductors with spin-orbit
coupling (NSC), including CePt3Si, UIr and Cd2Re2O7. We find that Delta(k) =
chi(k) t(k), where chi(k) is an even function which transforms according to the
irreducible representations of the crystallographic point group and t(k) is a
model dependent phase factor. We consider tunnelling between a NSC and a
conventional superconductor. It is found that, in terms of thermodynamical
properties as well as the Josephson effect, the state of NSC resembles a
singlet superconducting state with gap function chi(k).

Superconductivity