Tesco, Britain's biggest supermarket group, whose credit rating was cut to "junk" status by Moody's and S&P in January, is battling to recover from an accounting scandal and reverse its market share losses in Britain to discount chains Aldi and Lidl. The sale of the South Korean unit is the biggest divestment Tesco is making to improve its financials. An Aug. 24 report by Macquarie Research said Tesco's disposal of its South Korean business could bring the British retailer back into investment grade territory two years ahead of the brokerage's current estimates.