Yes, FERMIS is a Scrabble word!

Letter values in Scrabble US: F 4, E 1, R 1, M 3, I 1, S 1.

Is it a valid word?

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

a metric unit of length equal to one quadrillionth of a meter
Italian nuclear physicist (in the United States after 1939) who worked on artificial radioactivity caused by neutron bombardment and who headed the group that in 1942 produced the first controlled nuclear reaction (1901-1954)

Also: enrico fermi.

Not playable in Scrabble US: FEMTOMETER, FEMTOMETRE.