Jefferies is the world’s fifth-largest investment bank. - Jeenah Moon/Bloomberg News Wall Street’s Jefferies Financial Group and Japan’s Sumitomo Mitsui Financial Group are bolstering their ties in a push to court more companies and private-equity firms globally with their services on mergers and acquisitions, borrowing and investing money, and other work. The details SMFG’s commercial banking subsidiary, SMBC, has agreed to increase its equity ownership in Jefferies to up to 20% in the open market, fro ...