Elastic Anomalies at the First Order Transition in Lu5Ir4Si10

Ultrasonic measurements on a single crystal of the intermetallic compound Lu5Ir4Si10 are presented. Large anomalies in the velocity and ultrasonic attenuation of the elastic modes are observed at the structural phase transition T-S similar to 80 K. The velocity of the longitudinal C-11 and C-33 mode exhibits a second order transition behavior. In contrast the velocities of the shear C-44 and C-66 modes exhibit a first order transition behavior. The longitudinal C-11 mode is strongly coupled to the ordering system below T-S. Similarities in the longitudinal elastic anomalies with known reduced dimensional charge density wave systems suggest that the nature of the structural phase transition T-S in Lu5Ir4Si10 could be associated with a charge density wave phase transition.