Spin glass behavior of insulating K0.8Fe2-xS2
  We report the discovery of KxFe2-yS2 single crystals, isostructural to KxFe2-ySe2 superconductors. The sulfide compound is a small gap semiconductor and shows spin-glass behavior below 32 K. Our results indicate that stoichiometry, defects, and the local environment of FeCh (Ch = S,Se) tetrahedra have important effects on the physical properties of isostructural and isoelectronic KxFe2-yCh2 compounds. 
Hechang Lei, Milinda Abeykoon, Emil S. Bozin, and C. Petrovic
cond-mat.supr-con cond-mat.mtrl-sci cond-mat.str-el