Yes, MATERIALS is a Scrabble word!

Letter values in Scrabble US: M 3, A 1, T 1, E 1, R 1, I 1, A 1, L 1, S 1.

Is it a valid word?

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

the tangible substance that goes into the makeup of a physical object
information (data or ideas or observations) that can be used or reworked into a finished form
artifact made by weaving or felting or knitting or crocheting natural or synthetic fibers
things needed for doing or making something
a person judged suitable for admission or employment