X-Ray-pure samples of the solid solutions (Ce1-xLax)RuSn were obtained up to x=0.5. Powder diffraction data show the CeRuSn-type superstructure up to x ≈ 0:3 and the CeCoAl-type subcell for higher lanthanum contents. The structure of a single crystal with x=0.5 was refined on the basis of single-crystal X-ray diffractometer data: CeCoAl type, C2=m, a=1160.8(2), b=477.6(1), c=511.6(1) pm, β = 102:97(2)°, wR=0.0510, 444 F2 values, 20 variables. Magnetic investigations were performed for all samples up to a lanthanum content of x=0.4. No cooperative phenomena could be observed, and all samples show Curie-Weiss behavior above a certain temperature. The cerium valence is about 3.32(2) for all samples of the solid solution. Hence, La3+ has to replace Ce3+ as well as Ce4+ in a particular quantity. The electrical resistivity measurements confirm the suppression of the magnetic ordering and the structural transition upon replacement of cerium by lanthanum. 119Sn Mössbauer spectra of samples with x=0.2 and 0.5 are indicative of single tin sites with isomer shifts of δ =1.86(1)mm s-1 for x=0.2 and δ =1.88(1)mm s-1 for x=0.5. Both signals are subject to significant quadrupole splitting, a consequence of the low site symmetry. Results of XANES measurements are perfectly in line with the cerium valences determined by susceptibility measurements and yield a constant value of 3.16(1) for all investigated compounds
Pressure-induced structural transition and huge enhancement of superconducting properties of single-crystal Fe0.99Ni0.01Se0.5Te0.5 unconventional superconductor
