Intermetallic compounds of the binary systems Ta&sngbnd;Sn and Nb&sngbnd;Ge were formed on Ta or Nb wires by the method of vapor phase diffusion at elevated temperatures. Critical temperatureTc, critical magnetic fieldHc2at 4.2°K, and composition of these layers were measured as a function of heating conditions. Ta&sngbnd;Sn diffusion layers prepared at temperatures between 800° and 1200°C consisted predominantly of the A15 compound Ta3Sn with a lattice parameter ofa= 5.278 Å. The observed layer thickness was always less than 1 &mgr;. Simultaneous maxima inTc(7.0°K) andHc2(50 kOe) were measured on wires heated at 950°C for 3 days. On the other hand, in the Nb&sngbnd;Ge system the A15 compound Nb3Ge did not form in the same temperature range. The layers, of thickness from 1 to 20 &mgr;, consisted only of NbGe2for a diffusion temperature of 800°C, Nb3Ge2for 1200°C, and a mixture of the two at 1000°C. ConsequentlyHc2at 4.2°K for these samples did not exceed 12 kOe.