The electrical properties and optical absorption (OA) spectra of undoped BaSi2 films grown by molecular beam epitaxy were investigated The electron density and mobility of BaSi2 grown epitaxially on Si(111) were 5 x 10(15) cm(-3) and 820 cm(2)/V(.)s at room temperature, respectively. The conduction-band discontinuity at the BaSi2/Si heterejunction was estimated to be 0.7 eV from the current-voltage characteristics of n-BaSi2/n-Si isotype diodes. OA spectra were measured on polycrystalline BaSi2 films grown on transparent fused silica substrates with predeposited polycrystalline Si layer. The indirect absorption edge was derived to be 1.3 eV, and the optical absorption coefficient reached 10(5) cm(-1) at 1.5 eV. (c) 2005 Elsevier B.V. All rights reserved.