ELASTIC PROPERTIES OF CERU2

We present data of the elastic properties of the Laves phase compound CeRu2 in the normal and superconducting state obtained from ultrasound measurements. In the temperature range between the superconducting tr ansition temperature of 6.1 K and 300 K we used a deformation potentia l coupling approach to describe the temperature dependence of the elas tic constants. The elastic anomalies in the superconducting state are characterised with the model of thermally assisted flux flow (TAFF). T his enables us to construct a detailed superconducting B-T phase diagr am including the vortex dynamics and interpret the peak effect region. Especially the ultrasonic measurements exhibit clearly the connectin between the normal state and the superconducting properties. They slow that structural fluctuations have strong effects on the superconducti vity and on the vortex dynamics.