First phase nucleation in silicon–transition-metal planar interfaces

What is the first compound that nucleates in planar solid silicon–transition-metal binary couple reactions whose members form bulk equilibrium compounds? We propose, for couples annealed at low temperatures, the following simple rule: The first compound nucleated in planar binary reaction couples is the most stable congruently melting compound adjacent to the lowest-temperature eutectic on the bulk equilibrium phase diagram. The predictions of this rule are compared with experimental results.