This Letter describes the precipitation of gold in silicon from a highly supersaturated solution. After saturation of float-zone Si at 1275°C with gold, annealing experiments were performed at 850°C for various annealing times. By means of high-resolution electron microscopy, small particles (10–20 nm diameter) consisting of a metastable gold silicide were found. From selected-area diffraction patterns we deduce an orthorhombic unit cell witha= 0·960,b= 0·768 andc= 0·690 nm.