New synthesis route to and physical properties of lanthanum monoiodide.

A fast procedure to produce LaI by reduction of LaI2 or LaI3 in a Na melt under argon at 550 degrees C is given. The structural studies performed by means of powder X-ray diffraction as well as transmission electron microscopy are consistent with previous single-crystal results. Measurements of the electrical resistance on polycrystalline samples reveal metallic behavior for LaI in the range 10-300 K. Upon cooling, a small maximum in the resistivity has been observed at 67 K. This anomaly disappears upon heating a sample, however, yielding a hysteresis in rho(T) above 70 K. From the Pauli susceptibility, an electron density of states at the Fermi level of about 0.3 eV(-1).formula unit(-1) has been estimated, as compared with a value of 1.0 eV(-1).formula unit(-1) derived from ab initio LMTO band structure calculations.