Ordinary Shapiro steps were observed in the I - V curves of biepitaxial Josephson junctions at when microwave radiation at f = 11 GHz was applied to the junction. However, pronounced current steps were observed at twice the period, when the d.c. Josephson current was suppressed by high power microwave radiation. The extension of the voltage region, within which the double period steps were seen, increased with microwave power. Modified biepitaxial heterostructures of , with as a seed layer and as an intermediate buffer layer were grown by laser ablation on . The I - V characteristics for the biepitaxial Josephson junctions agreed well with the RSJ model for T > 50 K but showed hysteresis at T < 30 K. No large excess current was observed. The critical current density, about at 4 K, was an order of magnitude higher than for bicrystal junctions and prevalent biepitaxial junctions with a misorientation between the crystal planes on either side of the grain boundary. An irregular magnetic field dependence of the critical current, , indicated an uneven current distribution within the junction. The products for the junctions were about 1.5 mV at 4.2 K and 20 - 60 at 77 K. Pronounced current steps in the I - V dependencies due to a.c. Josephson current coupling to self-induced electromagnetic modes at the biepitaxial boundary were used to characterize the junctions.