A chemically-related but functionally distinct group of compounds are the ternary transition metal chalcogenide halides, such as (TaSe 4 ) 2 I and (NbSe 4 ) 3.33 I, both of which host charge density wave (CDW) behavior. The halides are quasi-one-dimensional materials with parallel (TaSe 4 ) n or (NbSe 4 ) n chains intercalated by iodine ions, further pushing down the dimensionality. Ta and Nb ions have alternating 4+ and 5+ valence, thus leaving the (TaSe 4 ) n or (NbSe 4 ) n chains with partially-filled conducting d bands, and resulting in a semiconducting behavior with shallow band gaps which can be possibly tuned.