Today the magnetic properties of multilayers and nanostructures including a metal or an insulator as a nonmagnetic spacer layer are rather well understood. But they are much more controversial for semiconductor spacers. For instance, for Co/Si multilayers short period coupling oscillations are predicted by ab initio computations but have yet to be observed. Here we show in Co/Si multilayers prepared at low temperature (90 K) strong saturation field oscillations that are consistent with the predicted coupling oscillations. However, the decay length of the oscillations is much longer than the expected one and cannot be explained within the framework of available theories.