A NEW TIN NIOBIUM SELENIDE SUPERCONDUCTOR

The new selenide SnNb5Se9 has been synthesized and characterized by de nsity measurements, X-ray powder diffraction. The cell, determined by U-Fit software, derives from that of NbSe2; it presents a superstructu re and an important disorder along the c axis, a single crystal study confirms these points. Mossbauer studies show three types of Sn atom. Magnetic properties show a superconducting behavior at 17.1K with part ial derivative H-c1/partial derivative T = 71 G.K-1 and partial deriva tive H-c2/partial derivative T = 5 kG.K-1.