Low-temperature specific heat ofC60

We have measured a large specific heat of polycrystalline ${\mathrm{C}}_{60}$ from T=1.4 to 20 K. The data were adequately fitted by a model containing Debye terms, Einstein oscillators, and a linear contribution. An analysis incorporating both vibrational and strongly coupled rotational degrees of freedom expected for the simple-cubic structure at low temperatures is proposed. We also discuss a possible interpretation based on a fairly narrow feature in the excitation spectrum. The large linear term may be a consequence of disorder resulting in a distribution of two-level tunneling centers.