MAGNETOELASTIC ANOMALIES IN CENISN

In this report, we present ultrasonic data of a CeNiSn single crystal with metallic low-temperature resistivity. The thermal variations of t he elastic constants at high temperatures can be described by a two-ba nd model using the deformation potential coupling approach. At very lo w temperatures, we observe a minimum in the field dependence of c(11) and c(33) accompanied by a maximum in the ultrasonic absorption. This may be a hint for a metamagnetic-like transition which is a frequent p henomenon in magnetically non-ordered heavy-fermion compounds.