Thermal Properties of Two Dimensional Mott System La _{1.17 -x}Sr_xVS _3.17

Experimental studies on physical properties of the two dimensional strongly correlated electron system La1.17-xSrx VS3.17 have been carried out. In the x region around 0.17, where the V-valency is similar to +3, the system is considered to be in a Mott insulating phase. With increasing x up to the region greater than or similar to 0.3, it becomes essentially metallic. Measurements of the thermal dilatation and the ultrasonic velocity have presented experimental evidence that a certain type of lattice distortion is involved in the phase transition observed previously by magnetic studies for samples with x similar to 0.17. The electronic specific heat coefficient gamma seems not to be enhanced as the system approaches the metal-insulator phase boundary from the metallic side.