Observation of Anomalous Heat Capacity in LiquidHe3near the Superfluid Transition

The specific heat of liquid ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ from 0.8 to 20 mK at zero pressure has been measured. Above ∼ 3 mK the specific heat is linear in temperature and $\frac{C}{\mathrm{nRT}}=2.11\mathrm{}$ ${\mathrm{K}}^{-1\mathrm{}}$, which is 30% less than the currently accepted value. Below 3 mK, $C$ appears to deviate increasingly from this relationship reaching, at the superfluid transition $T_c=1.04\mathrm{}$ mK, a value 9% in excess of the extrapolated linear specific heat. This Letter discusses the anomalous behavior and its consequences with regard to the interpretation of our data.