09-02U

Recently proposed four-sublattice model for Rochelle salt is enhanced by taking into account piezoelectric interactions with shear deformations. Spontaneous polarization, components of static dielectric permittivity tensor for both mechanically clamped and free crystals, their piezoelectric characteristics and elastic moduli are derived in the mean field approximation. A proper choice of model parameters provides a good quantitative description of the available experimental data. A comprehensive study of transverse field effect on phase transition temperatures, dielectric and elastic properties of Rochelle salt has been performed for the first time.