The propagation of shear horizontal (SH) wave is studied in a tri-material composed of a piezomagnetic layer and two semi-infinite piezoelectric half-spaces. These materials are hexagonal (6mm) crystals. A dispersion relation is exactly derived. The numerical results show the existence of the SH wave and its dispersion characteristics. These may be useful for the applications of piezoelectric-piezomagnetic media in the microwave technology.