H. Figueroa, J. M. Gracia-Bondia, F. Lizzi, J. C. Varilly A nonperturbative form of the spectral action principle in noncommutative geometry (42K, LaTeX) ABSTRACT. Using the formalism of superconnections, we show the existence of a bosonic action functional for the standard $K$-cycle in noncommutative geometry, giving rise, through the spectral action principle, only to the Einstein gravity and Standard Model Yang--Mills--Higgs terms. It provides an effective nonminimal coupling in the bosonic sector of the Lagrangian.