1. The nucleation theory of the refining of primary silicon crystals in hypereutectic Silumins microalloyed with phosphorus was verified by experiments. Particles were observed in silicon crystals (possible AIP) which served as additional centers of nucleation of primary silicon crystals. 2. Combined modification of high-silicon Silumins with phosphorus and sodium leads to refining of primary and eutectic silicon. 3. Modification with phosphorus is most expedient with phosphorus-containing salts, especially sodium phosphates.