After soaring 466 per cent in its Shanghai trading debut on Monday, ChangXin Memory Technologies (CXMT) became the most valuable company on mainland China’s stock market – the first semiconductor firm to hold the top spot in the market’s 35-year history. The state-backed maker of memory chips saw its market capitalisation surpass 4 trillion yuan (US$592 billion) on Friday amid a broader chip stock surge. It first ascended to the top of the list on Monday, ending its first trading day with a...