Crystal structure of R3Pd25-xB8-y, R = La, Ce

New ternary compounds La3Pd25-xB8-y (x=1.75, y=0.07) and Ce3Pd25-xB8-y (x=1.25, y=2.00) have been synthesized by arc melting. Their crystal structures were determined from X-ray single crystal diffraction data. Both compounds crystallize with a new monoclinic structure type, space group P21/c with a=1.17567(2) nm, b=1.05757(2) nm, c=1.60664(3) nm, β = 102.1788(10) deg, RF2=0.030 for 7427 structure factors and 289 variable parameters for La3Pd25-xB8-y and a=1.17453(3) nm, b=1.04571(3) nm, c=1.59759(5) nm, β=102.132(2) deg, RF2=0.035 for 2805 structure factors and 283 variable parameters for Ce3Pd25-xB8-y. Rietveld refinement for the X-ray powder diffraction patterns for both compounds confirmed the structure models determined from X-ray single crystal diffraction data.