In 2008, palladium traded under two hundred dollars an ounce.
Twelve years later it went over two thousand eight hundred.
Then it fell by more than half.
That is the entire case for platinum and palladium in a retirement account, and also the entire case against it, depending on which part of the sentence you stop reading.
The legal answer is simple. Yes, a precious metals IRA can hold platinum and palladium alongside gold and silver. Same account. Same custodian. No special permission.
The practical answer takes longer, because these two metals are not what most people think they are. They are not precious metals that happen to be industrial. They are industrial metals that happen to be precious, and that ordering matters enormously when you are 64 and drawing down an account.