June 23 (Reuters) - Miner and trader Glencore Plc GLEN.L said on Friday it had submitted an improved proposal to buy Australian miner Rio Tinto's RIO.AX , RIO.L stake in Coal & Allied Industries Ltd for $2.675 billion in cash plus a coal price-linked royalty. improved offer from Glencore comes three days after Rio Tinto selected Yancoal YAL.AX on Tuesday to buy its Coal & Allied division in Australia for $2.45 billion.