2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/165162We show that the pairing on de Rham realizations of 1-motives in "Theorie di Hodge III", IHES 44, can be defined over any base scheme and we prove that it gives rise to a perfect duality if one is working with a 1-motive and its Cartier dual. Furthermore we study universal extensions of 1-motives and their relation with $\natural$-extensions.21 pages. Last section rewritten. New proofsAlgebraic Geometry14L15text