Resistivity anisotropy of the misfit layer compound (SmS)1.25 TiS2

The misfit layer compound (SmS)1.25 TiS2 has a layered structure which consists on an alternating sequence of one |SmS| bi-layer adopting a NaCl distorted structure and one |TiS2| tri-layer with the Ti atoms plane sandwiched by two sulfur ones and the Ti atoms octahedrally coordinated. Stacking is along the c-axis. Each of these two subsystems has its own 3D lattice and space group, and they have a common (b*, c*) plane in the reciprocal lattice so that the a axes are parallel and of irrational ratio. The physical properties of this compound have never been investigated. Accurate resistivity anisotropy measurement down to the liquid nitrogen temperature is presented here.

The in-plane resistivity shows an anomaly at 202 K, and the out-of-plane resistivity shows also anomalies at 202 and 222 K and an upward curvature between 100 and 222 K. Consequently, the resistivity anisotropy shows peculiarities; mainly an important jump at 222 K.This behavior is discussed in the framework of a possible magnetic ordering and/or anisotropic lattices distortions. Although, the role of this work is to draw the attention to these features and further investigations to confirm these results would be of interest.

Further investigations are needed, mainly magnetic and crystallographic in function of temperature in order to conclude definitely whether there is any phase transition or not.