  Extended x-ray absorption fine-structure (EXAFS) measurements have been
carried out on Ni$_{50}$Mn$_{35}$Sn$_{15}$ in the austenitic and martensitic
phase. The temperatures associated with structural and magnetic phase
transformations are obtained from magnetization measurements. The system orders
ferromagnetically below 319 K while the structural phase transition occurs at
T$_M$ $\sim$ 200 K. EXAFS measurements have been carried out at Mn and Ni
K-edges and changes associated with respect to the local structure of these
absorbing atoms are compared. Significant changes in the nearest neighbour
interactions are seen as the system transits to the low temperature martensitic
phase. EXAFS provides evidence for local structural distortion even in the
cubic phase that is not seen from the x-ray diffraction studies. The results
obtained are understood in terms of changing hybridization between the
constituent atoms that influence the electronic structure at the Fermi level,
associated with the austenitic-to-martensitic transition.
