2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/65943We characterize the SDP designs that give rise to four-weight spin models with two values. We prove that the only such designs are the symplectic SDP designs. The proof involves analysis of cardinalities of intersections of four blocks.11 pagesCombinatorics05B05 (Primary) 7M25 (Secondary)text