BSTRACTHerein

we critically assess magnetotransport in the MAX phases and their 2D derivatives

MXenes. For some MAX phases

a simple

2D hexagonal metal model describes weak-field magnetotransport of their nearly free electrons reasonably well. For others

experimental and/or theoretical Fermi surfaces need to be mapped—a crucial task required for true understanding. Even less is known about MXenes. The density of apparent mobile carriers in Ti

3

C

2

T

x

—assuming a single-band model—is ≈1 × 10

14

 cm

−2

(10

28

 cm

−3

)

which justifies it being sometimes described as a 2D metal. Much work is needed before a clearer picture emerges.