Specific heat study of /spl alpha/-(BEDT-TTF)/sub 2/MHg(SCN)/sub 4/

Summary form only given. The /spl alpha/-phase of (BEDT-TTF)/sub 2/MHg(SCN)/sub 4/ exhibits several interesting physical properties at low temperatures. M=K, Rb, Tl salts show an anomalous phase transition around 10K both in transport and magnetic susceptibility of which origin has not yet clarified. In order to investigate nature of this phase transition and the low-temperature phase from a thermodynamic viewpoint, we performed specific heat measurements by adiabatic method for about 10 /spl tilde/ 20mg of samples. Our preliminary measurements down to about 2K give a value below l0mJ/(mol K/sup 2/) for M=Rb salts, which suggests that the electron-electron interaction in these compounds is weaker than that of /spl kappa/-phase compounds. More details including magnetic field dependence and search for possible anomaly in the transition will be discussed at the conference.