In the present contribution, the first attempt to produce Fe-Si nanoparticles by the laser-induced pyrolysis of iron pentacarbonyl vapours and silan gas is presented. The essential novelty of the process lies in exploiting the silan gas both as silicon donor and as sensitiser to ignite and sustain the reaction. Depending on the main reaction parameters. ultrafine and amorphous powder particles with an average size ranging between 15 and 20 nm, and with a relative iron content in between 25 and 75 at.% could be produced. Microstructural and magnetic characterisations showed that each particle is composed of intimately mixed iron and silicon-silicon oxide nano-islands with an average dimension of few nanometers. The amorphous particles exhibit a superparamagnetic behaviour both at room and at 5 K temperatures. (C) 2002 Elsevier Science B.V. All rights reserved.