[en] We report the synthesis of biphasic Pb (46 at.%)-Sn (54 at.%) nanoparticles dispersed in an aluminum matrix and explore the nature of the superconducting transition in these particles. The nanoscaled Pb-Sn alloy particles were dispersed in Al by rapid solidification and the two-phase nature of these particles was characterized by transmission electron imaging, diffraction and composition mapping. A weak superconducting transition occurs at 3.1 K in these alloys, which is much lower than the T_C expected for a Pb₄₆Sn₅₄ alloy or that due to the proximity effect between Pb and Sn. We show that it is the superconducting Al matrix with T_C = 1.2 K that plays a major role in determining the effective transition temperature of the system