A novel family of two-dimensional oxosilicate and mixed-oxosilicophosphate compounds, La4Ti5Si4-xPxO(22) (chi = 0, 1), has been synthesized and structurally characterized. The X-ray single-crystal structure analysis shows that the chi = 0 phase adopts a monoclinic lattice with a = 13.621(4) Angstrom, b = 5.673(3) Angstrom, c = 11.143(2) Angstrom, beta = 100.59(2)degrees; C2/m (No. 12); Z = 2. The unit cell, a chevkinite type, consists of alternately stacked lanthanum and single-layer (m = 1) titanium oxide, TiO2 (rutile), slabs. The La4Ti5Si4O22 phase represents the first member (m = 1) of the mixed-valence lanthanum titanium(III/IV) oxosilicate series, La4Ti(Si2O7)(2)(TiO2)(4m) This framework can be viewed as a rutile lattice that is sliced along the [110] plane at various thicknesses, m. The Ti-Ti distances across the shared octahedral edges in the rutile slab are uniformly spaced at 2.84 Angstrom (=b/2), in contrast to the distorted Ti-Ti distances observed in the higher member (m = 2) of the series. Four-probe,resistivity measurements on pressed pellet samples of the bulk chi = 0 and 1 phases show sharp increases in resist : at 13 and 90 K, respectively, which can possibly be attributed to the bipolaron formation. The structure and electrical property correlation is briefly discussed.