Nonlinear Susceptibility: A Direct Test of the Quadrupolar Kondo Effect   in UBe(13)
  We present the nonlinear susceptibility as a direct test of the quadrupolar Kondo scenario for heavy fermion behavior, and apply it to the case of cubic crystal-field symmetry. Within a single-ion model we compute the nonlinear susceptibility resulting from low-lying \Gamma_3 (5f^2 and Kramers (5f^3) doublets. We find that nonlinear susceptibility measurements on single-crystal UBe_{13} are inconsistent with a quadrupolar 5f^2 ground-state of the uranium ion; the experimental data indicate that the low-lying magnetic excitations of UBe_{13} are predominantly dipolar in character. 
A.P. Ramirez (ATT), P. Chandra (NECI), P. Coleman (RUTGERS), Z.Fisk   (LANL), J.L. Smith (LANL) and H.R. Ott (ETH)