Compounds Dy3Ag2.3Al8.7, Ho3Ag2.1Al8.9, Dy3Cu2.6Al8.4 and Ho3Cu2.4Al8.6 as new representatives of the La3Al11type structure

The crystal structure of compound Dy3Ag2.3Al8.7 has been determined using X-ray single-crystal diffraction. It has the La3Al11type structure with a partially ordered atomic distribution: space group Immm, a=0.4302(1), b=1.2530(4), c=0.9981(2) nm, 410 unique hkl reflections with Fhkl>4SIGMAFhkl, RF=0.027, RW=0.042. The same structure type has been established for the new compound Ho3Ag2.1Al8.9 (a=0.42983(3), b=1.25215(7), c=0.99721(5) nm, RI=0.087, RP=0.132) and two earlier known compounds Dy3Cu2.6Al8.4 (a=0.42125(3), b=1.2432(1), c=0.98267(8) nm, RI=0.087, RP=0.114); Ho3Cu2.4Al8.6 (a= 0.41962(1), b=1.23946(5), c=0.98070(4) nm, RI=0.079, RP=0.103) using X-ray diffraction.