AustralianSuper has raised its long-term bet on battery minerals company Syrah Resources, after agreeing to subscribe for more shares in the graphite miner, loan the company money and potentially underwrite part of its fifth capital raising in less than four years.

The emphatic show of support from the nation's biggest pension fund for the ASX's most shorted stock reflects AustralianSuper's strategy to ''partner'' with companies rather than just invest, and comes despite the fund's existing 15 per cent stake in Syrah being underwater at the miner's current share price.