SHANGHAI, Jan 5 (Reuters) - China’s central bank on Tuesday lifted its official yuan midpoint by the most since it abandoned a decade-old peg against the dollar in 2005, underpinned by sharp gains in spot prices a day earlier. The People’s Bank of China (PBOC) set the midpoint rate at 6.4760 per dollar prior to the market open, 648 pips, or 1.0%, firmer than the previous fix of 6.5408. Tuesday’s official guidance, the strongest in more than 30 months, also came in higher than Reuters’ estimate of 6.4978. Moves in the midpoint was the biggest one-day strengthening in percentage terms since July 2005, when China revalued the yuan and took it off a fixed dollar peg.