La2Sb, a layered superconductor with metal-metal bonds
  We found La2Sb with a layered structure composed of alternate stacking of La square nets and LaSb layers exhibits bulk superconductivity with a critical temperature of 5.3 K. This suggests that the presence of the square net with strong La-La metal bonding is essential for the emergence of superconductivity. 
Hiroshi Mizoguchi and Hideo Hosono
cond-mat.supr-con