Lewis, a former Unilever executive who joined Tesco in September, has made broad changes, closing more than 40 stores, cutting thousands of jobs and selling noncore assets. He has also put his top executives on the floor at certain stores to help understand and improve the customer experience. Tesco has steadily lost market share in recent years to discount retailers like the German grocers Aldi and Lidl, and it has faced pricing wars with its British rivals. It has also been mired in investigations concerning a £263 million overstatement of profit. The retailer recorded a loss of £6.4 billion last year, its worst ever. The Homeplus deal would reduce Tesco's debt by £4.2 billion, but still leave it with about £17.5 billion in debt. The transaction also represents the latest global retrenchment by Tesco in recent years.