Alternating reaction phases in Sn-Cu/Ni-Co solid-state reactions

► An unusual alternating phenomenon, CoSn2/Ni3Sn4/CoSn2/Ni3Sn4/…, was found. ► The alternating phenomenon was attributed to the small mobility of Ni. ► 10 at%Co addition does not alter the reaction path of the Sn-Cu/Ni couples.