  Reciprocity is when the scattering amplitude of wave propagation satisfies a
symmetry property, connecting a scattering process with an appropriate reversed
one. We report on an experiment using nuclear resonance scattering of
synchrotron radiation, which demonstrates that magneto-optical materials do not
necessarily violate reciprocity. The setting enables to switch easily between
reciprocity and its violation. In the latter case, the exhibited reciprocity
violation is orders of magnitude larger than achieved by previous wave
scattering experiments.
