While plasmonics has seen numerous striking experimental results during the last decade, there is only very few dealing with nonlinear integrated plasmonics. This last research topic addresses photonic devices in which waveguide aspects are predominant and nonlinear effects emerges from bulk term. Our current work belongs to this difficult but promising topic. We have obtained the first experimental proof of the coupling between a plasmon and a spatial soliton. This demonstration have been realized in a layered planar structure where the nonlinear layer is made of a specific chalcogenide glass ensuring both a high nonlinear coefficient, a low two-photon absorption, and a relatively high power damage threshold. In its plasmonic part, the chalcogenide layer is separated from the 32 nm thick gold layer by a 10 nm thick silica layer whom the thickness was optimized by modal numerical simulations in order to ensure a high effective nonlinearity of the plasmonic structure. Our experimental results reveal a strong reinforcement of the self-focusing of the incident beam only when it passes through the plasmonic part of the structure. This effect occurs when TM polarized waves are launched while no reinforcement is observed when TE polarized waves are considered. This is one of the signatures of the plasmon-soliton coupling. Power dependency of the recorded spatial profiles has also been studied together with the impact of the localization of the plasmonic structure relatively to the input facet of the light beam. In order to get a better understanding of these phenomena, we have build a spatial nonlinear propagation model taking into account two spatial dimensions and the different field profiles along the full structure (with/without the gold layer). We get a good agreement between the experimental data and the numerical results.