Saddle solutions for a class of systems of periodic and reversible semilinear elliptic equations.

We study systems of elliptic equations -Delta u(x)+F-u(x,u) = 0 with potentials F is an element of C-2 ( R-n, R-m) which are periodic and even in all their variables. We show that if F(x, u) has flip symmetry with respect to two of the components of x and if the minimal periodic solutions are not degenerate then the system has saddle type solutions on R-n.