Lifshitz points in uniaxial ferroelectrics

The critical behavior of Lifshitz points in systems with short range and uniaxial dipolar interaction is calculated. These multicritical points belong to a new universality class and may be relevant in the phase diagram of ${\mathrm{Sn}}_2$ ${\mathrm{P}}_2$(${\mathrm{Se}}_{\mathit{x}}$ ${\mathrm{S}}_{1\mathrm{-}\mathit{x}}$ ${)}_6$. A variety of combinations of spatially anisotropic critical behavior is possible. The critical effects in the elastic constants are briefly mentioned.