GdSi2and ErSi2polycrystalline thin films were studied using electrical resistivity in the temperature range 10–900 K, Hall effect from 10–300 K and reflectivity spectra from 0.2–100 &mgr;m at room temperature. Composition and structure in these films were investigated by Rutherford backscattering spectroscopy and x‐ray diffraction techniques. These silicides are metallic with (i) a remarkable difference in their residual resistivity, (ii) a phonon contribution to the resistivity which showed a negative deviation linearity, and (iii) low energy interband transitions. Resistivity data indicated that GdSi2and ErSi2have a Debye temperature of 328 and 300 K respectively and a limiting resistivity value much higher than that observed in other transition metal disilicides. The charge carrier concentration was estimated to be 4×1021cm−3at room temperature according to Hall measurements, and the mean free path was 63 A˚ and 320 A˚ for GdSi2and ErSi2, respectively, at 10 K. The parameters obtained by the optical analysis are in good agreement with those extracted from the transport measurements, thus permitting one to obtain a reasonable value for the Fermi velocity.