An intermetallic compound consisting of a very electropositive atom, such as sodium or potassium, and a less electropositive atom, such as zinc or germanium. An example of a simple Zintl phase is KGe. The properties of Zintl phases are intermediate between metals and ionic crystals, as they are brittle and poor electrical conductors. The phase is named after Eduard Zintl (1898–1941), who first investigated these compounds in the 1930s.