The investigated amorphous germanium-carbon multilayers are a novel system for the synthesis of germanium nanocrystals. The structure of the multilayers was studied by cross-sectional TEM and X-ray reflection. With increasing distance from the substrate, an increase of the interfaces roughness is detected. Roughening of interfaces is mainly ca;sed by germanium growth, whereas carbon smoothes the interfaces. Taking these effects into consideration, the simulated X-ray reflection spectra agree well with measured spectra. After annealing at 870 K, crystallization of the germanium sublayers is observed. The crystallite size is equal to the thickness of the Ge-layer in the range from 25 nm down to 3 nm, what is confirmed by X-ray diffraction and TEM.