We report the first measurements of the magnetic-field penetration depth λ in the heavy electron superconductor UBe13, performed using a SQUID magnetometer. We find the temperature dependence of λ(T)-λ(0) to follow a T2 law at low temperatures, giving further evidence of extreme gap anisotropy in this compound. We calculate the temperature dependence expected for a variety of anisotropic states, including those representing certain classes of "exotic" pairing. In general situations, the supercurrent is not parallel to the vector potential, and a more complicated field penetration takes the place of the normal Meissner effect. We argue that the data are consistent with an energy gap with point nodes on the Fermi surface but inconsistent with the large value of the Landau parameter F1S expected for a translationally invariant Fermi liquid with large effective mass. © 1986 Springer-Verlag.

We report the observation of a T2 temperature dependence of the magnetic field penetration depth in UBe13 at low temperatures. We show that this behavior is consistent with an anisotropic gap function for an axial P-wave state. Our results further show that the Landau parameter Fls appears to be small. © 1986 The American Physical Society.