Optical properties and phase composition of In-Au and Sn-Ag ultra-thin films grown by sequential evaporating and co-depositing of metals in a vacuum were investigated combining X-ray diffraction and spectroscopic ellipsometry methods. The atomic concentration ratios of bilayer and co-deposited samples were the same, i.e. In(Sn):Au(Ag) = 1:2. The XRD patterns indicated creation of AuIn, AuIn2, Au3In2, Au9In4 and Ag3Sn intermetallic compounds at room temperature. The effective complex dielectric functions of the composite layers, <(epsilon) over tilde (E)> = + i , were determined from ellipsometric quantities Psi and Delta measured in a photon energy range of 0.6-6.5 eV. The free-carrier parameters (unscreened plasma frequency and free-carrier damping) and optical resistivity were evaluated using a semiclassical Drude-Lorentz model of the effective dielectric function. There was noticed a distinct influence of phase composition and surface morphology on the optical constants and conductivity of the samples: rho(op) changed from approximately 15 mu Omega cm to 37 mu Omega cm for Ag-Sn structures, composed of beta-Sn and Ag3Sn phases, and from 21 mu Omega cm to 83 mu Omega cm for Au-In multiphase system. Lower resistivity demonstrated diffusive layers formed after deposition of an In(Sn) thin film on the noble metal underlayer. (C) 2010 Elsevier B. V. All rights reserved.