Metastable phase formations were studied in Au/a-Si thin film multilayers using differential scanning calorimetry and x-ray diffraction. Two nonequilibrium crystalline silicides were found to form below 500 K. Each phase formed by a different mechanism, and the competing growth of the two phases over the temperature range of 375 to 500 K, was found to depend greatly on thickness and grain size in the Au layers. At higher temperatures (500–600 K), these metastable phases decomposed and the a-Si crystallized by metal-induced crystallization to yield a phase mixture of Au and x-Si. The enthalpy of crystallization of a-Si was measured from the calorimetry data to be -12.1±1.2 kJ/mol. © 2002 American Institute of Physics.