Abstract Using a conduction calorimeter the specific heat critical behaviour of a TGS crystal has been measured. The ranges of the deviations from the classical behaviour below and above the transition point are 1 and 20 K respectively. These deviations seem to be well related to LK theory predictions. In a range of 0.1 K below the transition point thermal hysteresis appears which does not depend on the measuring temperature rate. The same behaviour is obtained with the sample at atmospheric pressure and under a high vacuum.
