The stake increase makes AustralianSuper the largest stakeholder in Pilbara with a 6.1% interest, overtaking a Ganfeng Lithium Group subsidiary, which owns 5.74%, according to LSEG data.
AustralianSuper maintained its position as the third-largest shareholder in Endeavour, building its stake up to 8.8% from 7.65%.
The country's largest pension fund, which manages over A$300 billion ($201.27 billion) of retirement savings, declined to comment on the stake increases.
AustralianSuper has, in the last few months, shifted its attitude towards investing in some of the country's largest companies, and is now actively scooping up stakes in blue-chip firms to give itself more leverage and control on strategy.
It bought Pilbara shares worth A$558 million in November last year, at a time when domestic lithium miners were being closely watched by global players as acquisition targets.
Endeavour, the country's biggest pub owner, is going through a board shake-up with Chair Peter Hearl resigning after a period of disagreement with top shareholder and billionaire publican Bruce Mathieson.
Pilbara and Endeavour did not immediately respond to Reuters' requests for comments.
($1 = 1.4905 Australian dollars)
(Reporting by Poonam Behura; Editing by Janane Venkatraman and Mrigank Dhaniwala)
