Shares of ChangXin Memory Technologies (CXMT), China’s leading DRAM maker, jumped 12 per cent on Monday to close at a record 61.80 yuan (US$9.16), lifting its market capitalisation to 4.13 trillion yuan and extending its lead as China’s most valuable listed company.The Hefei-based chipmaker first overtook Hong Kong-listed Tencent Holdings on Thursday as China’s most valuable listed company, when CXMT’s market value reached about 3.54 trillion yuan. It had already become the most valuable company on mainland exchanges on its July 27 trading debut, when the stock surged 466 per cent. Monday’s close left CXMT more than seven times above…