Formation of n-type pyrite thin films has been obtained by direct sulphuration from metallic Fe-Co bilayers of atomic ratio Fe/Co similar to 2.5, at temperatures between 250 degrees C and 500 degrees C. Pyrite structure is observed by X-ray diffraction measurements (XRD). Composition depth profile has been studied by Rutherford Backscattering Spectroscopy (RBS). Three different zones can be observed: a non-diffused Co layer near the substrate, a FeS2 layer with homogeneous diffusion of Co, and a Co-rich FeS2 layer on the surface. Co content seems not to be dependent on the sulphuration temperature. Electrical characterization gives values from - 17.4 +/- 0.9 mu V/K to - 67 +/- 4 mu V/K for the Seebeck coefficient and from (3.7 +/- 0.2).10(-3) to (2.1 +/- 0.1).10(-2) Omega cm for the resistivity, as sulphuration temperature is increased. Transport properties are compared with those of non-doped films and the Co distribution through the films will be analysed.