Anomalous specific heat of tau type organic conductors

Electronic states of τ-(EDO-S,S-DMEDT-TTF) 2 (AuBr 2 ) 1+y and its analogue τ-(P-S,S-DMEDT-TTF) 2 (AuBr 2 ) 1+y systems were studied by measurements of the specific heat in the temperature region from 0.1K to 80K. In some samples, we found large excess specific heat with a peak around 5K. It has Schottky type temperature dependence with energy gap of about 12K. The excess entropy corresponds to 50-70% of two level systems with Avogadro's number. These anomalous electronic states give us the crucial information of the peculiar properties of these systems.