The title compounds were prepared by reaction of the binary rare earth silicides LnSi(2) and the two-phase alloys "LnSi(3)" with nitrogen at high temperatures. The crystal structure of the compounds Ln(3)Si(6)N(11) was determined from single-crystal X-ray data of Sm3Si6N11 : P4bm, a = 999.7(1) pm, c = 483.6(1) pm, Z = 2, R = 0.010 for 757 structure factors and 38 variable parameters. The tetrahedral SiN4 groups are linked via corners, forming a three-dimensional network. The samarium atoms occupy two different cavities of that network both with eight nitrogen neighbors. The new compounds LnSi(3)N(5) (Ln = Ce, Pr, Nd) were found to be isotypic with the previously reported nitridosilicate LaSi3N5.