A new misfit bilayer compound in the samarium titanium sulfur system

The composite bilayer misfit compound (SmS)1.25(TiS2)2 was prepared and its structure determined via the composite approach by single crystal X-ray diffraction. This compound crystallizes with monoclinic unit cells (SmS subcell: a1 = 5.473(4) Å, b1 = 5.854(2) Å, c1 = 33.53(1) Å, α1 = 93.36(5) °, β1= 90 °, γ1 =90 °; TiS2 subcell a2 = 3.425(3) Å, b2 = 5.854(2) Å, c2 = 33.53(1) Å, α2 = 93.36(5) °, β2 = 90 °, γ2 = 90 °. The mismatch of periodicities occurs along the a-direction. The structure consists of an alternated stacking of SmS (NaCl structure type) and (TiS2)2 slabs along the c-direction. Presence of interstitial Ti atoms within the van der Waals gap between adjacent TiS2 layers is revealed. Thus, the stacking mode within the (TiS2)2 block is markedly different from that observed with misfit bilayer homologues such as (PbS)1.18(TiS2)2 or (SbS)1.15(TiS2)2 where no extra Ti atoms were found. Electrical transport measurements show a metallic behaviour down to 4.2 K. Magnetic study shows a behaviour mainly due to the Sm3+ van Vleck paramagnetic ion.