An attempt was made to grow BaSi2 epitaxial films on Si(001) substrates using molecular beam epitaxy. The structure and morphology of the films were investigated using reflection high-energy electron diffraction, X-ray diffraction, electron backscatter diffraction, atomic force microscopy, and transmission electron microscopy. The BaSi2 film grown was a-axis oriented, despite a large lattice mismatch. The measurements indicated that there are two possible epitaxial relationships of BaSi2(100)//Si(001) with BaSi2[010]//Si[110] and BaSi2[001]//Si[110], due to the fourfold symmetry of Si(001). X-ray reciprocal space mapping revealed that the BaSi2 film was almost strain-free. Plan-view transmission electron microscopy clarified the grain size and the existence of grain boundaries in the BaSi2 film. (c) 2012 Elsevier B.V. All rights reserved.