Interference between x-ray beams scattered from a nuclear resonance in stainless-steel foils of different thicknesses has been observed. In-phase and out-of-phase oscillations have been measured for yields with three different time windows, which exist because of a sign change of the amplitude describing the time evolution of the nuclear-resonant forward scattering. This confirms the amplitude modulation in subsequent decays brought about by x-ray dispersion in addition to the increase in the decay rate.