A magnetic semiconductor Si:Ce thin film was prepared using a vacuum evaporation system with electron-beam guns. The as-deposited thin film was amorphous and exhibited n-type conduction. It showed temperature dependence of resistivity (ρ–T), as in a normal semiconductor, and a diamagnetic property. By annealing at 973 K, however, the film epitaxially crystallizes and the conduction changes to the p-type. The resistivity of the film abruptly decreases by three orders of magnitude below 30 K, unlike that of the as-deposited film. The magnetic susceptibility measured at a low magnetic field (750 Oe) also decreases around the same temperature in ρ–T curves. These magnetic and carrier transport phenomena are responsible for the substitutionally dissolved Ce in Si. © 2002 American Institute of Physics.