Australia's biggest superannuation fund says the investment thesis that attracted it to Australia's most shorted stock remains intact, in a major vote of confidence for struggling graphite producer Syrah Resources.

Syrah shares have fallen by 94 per cent since June 2016 and its ability to outlast rival graphite producers through this year's downturn is largely due to support from AustralianSuper, which owns 16.5 per cent of the company and has acted as its underwriter and lender.