The anisotropy and temperature dependence of the magnetic-field penetration in superconducting ${\mathrm{UPt}}_3$ have been measured by muon spin relaxation. The extrapolated zero-temperature values for the penetration depths parallel and perpendicular to the c axis are ${\lambda }_{\mathrm{\parallel }}$=7070±30 Å and ${\lambda }_{\mathrm{\perp }}$=7820±30 Å, respectively. The temperature dependences of ${\lambda }_{\mathrm{\parallel }}$ and ${\lambda }_{\mathrm{\perp }}$ are different and can both be accounted for by a superconducting gap function with a line of nodes in the basal plane and axial point nodes.

• Received 14 May 1990

DOI:https://doi.org/10.1103/PhysRevLett.65.2062