RIYADH: Saudi Aramco’s Luberef refinery unit appointed Global Investment Bank and Financial Services, known as Citigroup, to join the list of banks to lead in its potential initial public offering, Bloomberg reported citing people familiar with the matter. Luberef plans to launch its IPO in the second half of the year aiming to raise more than $1 billion, the people said. According to the report, Aramco has already appointed the local unit of HSBC Holdings Plc and SNB Capital to advise on the offering. Luberef will join a number of Aramco subsidiaries already listed on Saudi Arabia’s stock exchange, including chemicals maker Saudi Basic Industries Corp. and Rabigh Refining. Jadwa, a Saudi-based investment firm, is expected to sell a 30 percent stake in Luberef during the IPO.