The transport and thermal properties of heavy-fermion superconductors are explained in terms of (i) an anisotropic order parameter with a line or lines of nodes and (ii) an effective mean free path which, except for the lowest temperatures, is approximately temperature independent and of a similar magnitude as in the normal state. Such a mean free path is shown to arise in a consistent treatment of impurity scattering close to the unitarity limit.

• Received 11 March 1986

DOI:https://doi.org/10.1103/PhysRevLett.57.2575