Precious metals miner Sibanye-Stillwater has been upgraded by Moody’s Investors Service to Ba2 with a positive outlook, with the agency citing the group’s disciplined capital allocation over the past two years.

The upgrade from Ba3 still has Sibanye-Stillwater in a category considered below investment grade, meaning that its business continues to have speculative elements. Ba2 is the second-highest speculative grade rating...