Yes, AMPS is a Scrabble word!

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

Is it a valid word?

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

the basic unit of electric current adopted under the Systeme International d'Unites
a nucleotide found in muscle cells and important in metabolism; reversibly convertible to ADP and ATP

Also: a, adenosine monophosphate, adenylic acid.