Continuous-wave photorefractive experiments in ${\mathrm{Sn}}_2{\mathrm{P}}_2{\mathrm{S}}_6$ crystals and interband photorefraction at the visible wavelengths of 514 and $488\mathrm{nm}$ are presented. Two-wave mixing and Bragg diffraction measurements at $514\mathrm{nm}$ show grating response times of around $100\mathrm{\mu }\mathrm{s}$ at moderate light intensities of $0.6\mathrm{W}∕{\mathrm{cm}}^2$ , i.e., 2 orders of magnitude faster than measured in the same crystal in the conventional photorefractive regime. A large two-wave mixing gain of up to $\Gamma =60\pm 8{\mathrm{cm}}^{-1}$ is measured, and holes are identified as dominant charge carriers for the interband photorefractive effect.