Yes, PALLIUMS is a Scrabble word!

Letter values in Scrabble US: P 3, A 1, L 1, L 1, I 1, U 1, M 3, S 1.

Is it a valid word?

PALLIUMS is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

the layer of unmyelinated neurons (the grey matter) forming the cortex of the cerebrum
(zoology) a protective layer of epidermis in mollusks or brachiopods that secretes a substance forming the shell
(Roman Catholic Church) vestment consisting of a band encircling the shoulders with two lappets hanging in front and back
cloak or mantle worn by men in ancient Rome

Also: cerebral cortex, cerebral mantle.