  We present a procedure for nonlinearity management of metal-dielectric
composites. Varying the volume fraction occupied by silver nanoparticles
suspended in acetone we could cancel the refractive index related to the
third-order susceptibility, $\chi_{eff}^{(3)}$, and the nonlinear refraction
behavior was due to the fifth-order susceptibility, $\chi_{eff}^{(5)}$. Hence,
in a cross-phase modulation experiment, we demonstrated for the first time the
effect of spatial-modulation- instability due to $\chi_{eff}^{(5)}$. The
results are corroborated with numerical calculations based on a generalized
Maxwell-Garnet model.
