Specific heat of the two dimensional antiferroelectric squaric acid

The heat capacity of a single crystal of the two dimensional antiferroelectric squaric acid was measured particularly near the phase transition. In a wide temperature range belowT _c a strong temperature dependence of the anomaleous specific heat is found which can be described by a critical exponent=0.5. The behaviour close toT _c is determined by a latent heat thus indicating the phase transition to be of the first order. Near the phase transition the thermal behaviour can be described by a Landau type theory. The smallness of the transition entropy detected may be ascribed possibly to proton tunneling.