Tetracyanamidosilicates of the type ARE[Si(CN2)(4)] with A=K, Rb, and Cs and RE=Y and La-Lu have been prepared by a solid-state metathesis reaction. The potassium compounds with RE=La-Gd crystallize orthorhombically in the space group P2(1)2(1)2. Rubidium as well as cesium compounds crystallize tetragonally in the space group I (4) over bar. The luminescent properties of ARE[Si(CN2)(4)]:Ln compounds with RE=Y, La, and Gd doped with 5 mol % Ln=Ce, Eu, or Tb were investigated. Temperature-dependent magnetic susceptibilities were measured for KGd[Si(CN2)(4)]. The value of the magnetic moment is 7.3 mu(B)/Gd3+ ion, which is in line with the expected value for the [Xe]4f(7) configuration of Gd3+.