By Ross Kerber (Reuters) – The Teamsters union wants four large U.S. retailers to investigate if companies in their supply chains are underpaying workers, hoping the retailers will use their leverage with vendors to achieve greater protection for those individuals. The union has filed resolutions for shareholder meetings this spring at Lowe’s Companies, Best Buy Co, TJX Companies and Urban Outfitters Inc, according to union officials and documents seen by Reuters. Only one, at Lowe’s, so far has been disclosed in public filings. They are among a wave of resolutions set to make “human capital m…