The paper reports on a novel surface plasmon resonance (SPR) substrate architect tire based on the coating la gold (Au) or silver (Au) substrate with 5 nm thin amorphous silicon carbon alloy films. Ag/a-Si1-xCx:H and Au/a-Si1-xCx:H multilayers are found to provide a significant advantage in terms of sensitivity over both Ag and Au for SPR refractive index sensing. The possibility For the subsequent linking of stable organic monolayers through Si C bonds is demonstrated. In a proof-of-principle experiment that this structure can be used for real-time biosensing experiments, amine terminated biotin was covalently linked to the acid-terminated SPR surface and the specific streptavidin biot in interaction recorded.