Neutron scattering data from the cubic heavy-fermion compound YbBiPt are presented, along with an interpretation in terms of strongly broadened crystal-field levels. To first order, the ground state is sixfold degenerate, consisting of a doublet (7) and quartet (8). Integration over these levels reproduces the observed linear specific-heat coefficient of 8 J mol -1 K -2 to within 20%. At the lowest temperatures, an extra symmetry-forbidden splitting is observed. © 1995 The American Physical Society.

The physical properties of YbBiPt are complicated because there are three competing energy scales all of order 1 K: the coupling energy between Yb moments as measured by the Néel temperature (TN), the splitting between the groundstate and first excited crystal electric field levels (TΔCEF) and the Kondo temperature (TK). The magnetically ordered phase below TN=0.45 K appears to be reduced local moment ordering that is incommensurate with the lattice. Associated with this order is the formation of a superzone gap that can be detected by electrical resistivity measurements. Attempts to treat TK and TΔCEF separately only account for gross features of the data presented. © 1994.