Fully oriented AlCuCo decagonal quasicrystalline films on crystalline substrates were successfully prepared by multitarget magnetron sputtering followed by postannealing. The width of the rocking curve competes with that of a single crystal. To explain the result, we suggest that the full orientation of the films originates from the fact that only one atomic flat plane of the structure is available to match the flat surface of the substrate, which gives a minimum interface free energy. ©1997 American Institute of Physics.