  We resolve the old riddle related to the critical behavior of the heat
capacity near the smectic A -- hexatic second order phase transition.
Experiment suggests a "large" positive specific heat critical exponent
inconsistent with the universality class for this phase transition implying the
very small negative exponent. We show that essential features of the heat
capacity for the smectic A -- hexatic phase transition can be rationalized in
the framework of a theoretical model treating jointly fluctuations of the
hexatic orientational order and of the positional (translational) order
parameters. Assuming that the positional (translational) correlation length is
larger than the hexatic correlation length, we calculate a temperature
dependence of the specific heat in the critical region near the smectic A --
hexatic phase transition. Our results are in a quantitative agreement with the
calorimetric experimental data.
