Point-contact spectra of the heavy-fermion superconductors UBe13and UPt3

We have measured the current-voltage characteristics of point contacts between U${\mathrm{Be}}_{13}$ or U${\mathrm{Pt}}_3$ and the normal metals W or Pt (metallic point contacts) or GaAs (Schottky-barrier tunneling contact) in the temperature range between 50 mK and 1 K. In the metal-point-contact characteristics ($\frac{\mathrm{dV}}{\mathrm{dI}}$ vs $V$) there appear zero-bias minima of width $2\Delta$ below $T_c$. The ratio $\frac{2\Delta }{k_B{T}_c}$ is close to the BCS value. The tunneling spectra of U${\mathrm{Pt}}_3$ exhibit weak additional structure below $T_c$. A value $2\Delta$ has been estimated, which is a factor of 2 larger than that for the metal point contacts.