The interface structure between silicon and silver after the eutectic reaction at 950-degrees-C has been examined primarily by using high-resolution transmission electron microscopy. Silver almost became a single crystal and a unique interface structure was found, where a special orientation relationship across the interface was recognized. The dominant relationship was obtained as {111}Ag parallel-to {111}Si and [110]Ag parallel-to [110]Si. The lattice arrangement model of the interface showed that the interface expressed by this relation has a good lattice match across the interface.