Unexpected Ferromagnetism in Alkaline-Earth Silicides

Alkaline earth mono-silicides (AESi, AE $=$ Ca, Sr, Ba) are poor metals and their transport properties are not solely determined by the Zintl anion, in contrast to their Zintl-type composition. Their conducting network is formed by the depopulated ${}^{1}_{\infty}$[Si$^{2-}$] $\pi$-system and AE-$d$ states. This justifies the special local coordination of the metal atoms and the planarity of the silicon chains. The low density of carriers seems to be a playground for magnetic instabilities and the triangular prismatic arrangement of AE atoms responsible for the observed weak glassy behavior.