2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/36547The Euler-Lagrange equations for some class of gravitational actions are calculated by means of Palatini principle. Polynomial structures with Einstein metrics appear among extremals of this variational problem.8 pages in LaTeX, to appear in Reports on Mathematical PhysicsGeneral Relativity and Quantum CosmologyMathematical Physicstext