Critical behavior of heat capacity of the SC(NH$_2)_2$ ferroelectric in the region of incommensurate phase transition

The anomalous (nonclassical) behavior of heat capacity in the region of the second-order phase transition «initial phase-incommensurate phase» was experimentally observed in the SC(NH$_2)_2$ ferroelectric. Such a critical behavior of heat capacity above and below the temperature of incommensurate phase transition is shown to be qualitatively consistent with the fluctuation theory of $XY$-type systems.