Anomalous Specific-heat of C-60

Measurements on the temperature dependence of the specific heat of pure C60 in the range 4 < T < 300 K are reported. A large hysteresis is observed between 165 and 270 K. On cooling, two peaks are observed, respectively, around 255 and 165 K. On heating, only one large peak is observed at 255 K. These results are tentatively discussed in terms of the dynamics of the C60 molecules in the crystal