[en] Within the framework of Cartan's generalization of Einstein's theory of gravitation one can achieve a unification of gravitational and weak interactions by appropriate choice of the parameter that couples spin and torsion. The proposed spin-torsion coupling has negligible cosmic effects except at stages of evolution when 10⁸¹ nucleons are confined to a sphere with a radius of about one astronomical unit. For a single nuclear particle the gravitational effects of mass and spin balance at a radius of about 1% of its Compton wavelength, thus stabilizing it against gravitational collapse. (author)