First measurements of the photoelectron yield excited by X-ray standing waves and of reflectivity curves are carried out under the conditions of three-beam 111/220 X-ray diffraction. A comparison of the experimental results with plane-wave dynamical theory calculations shows good agreement. It proves new dynamical interference effects predicted by the theory of multiple diffraction. The main of them are the effect of phase sensitivity of the reflectivity curves and the two-dimensional localization of atom positions in a crystal lattice.