HfSi2 polycrystalline thin films, grown by coevaporation of Hf and Si and subsequently annealed at 850-degrees-C, were studied by electrical resistivity measurements (from 10 to 900 K), Hall voltage (from 10 to 300 K), and optical reflectance (at room temperature) from 5 meV to 12 eV. Composition and structure of the films were investigated by Rutherford backscattering spectroscopy and x-ray diffraction. HfSi2 is metallic with (i) a high residual resistivity, (ii) a phonon contribution to the resistivity showing a negative deviation from linearity, and (iii) low-energy interband transitions. Transport measurements yielded a Debye temperature of 430 K, a free-carrier concentration of approximately 4 X 10(21) cm-3, and a mean free path of 139 angstrom. The reflectivity was Kramers-Kronig transformed to obtain the dielectric functions which, at low energies, are discussed in term of the Drude model. The optical parameters agree quite well with transport results, thus permitting one to obtain a reasonable value for the Fermi velocity
