The crystal structure of the new ternary compounds RE5Sb2X2 (RE—Y, Tb, Dy, Ho, Er, Tm; X—Si or Ge)

A series of novel ternary compounds RE5Sb2X2 have been synthesized via arc melting elemental metal ingots (RE—Y, Tb, Dy, Ho, Er, Tm, X—Si or Ge). The crystal structure was solved for Tm5Sb2Si2 from single crystal X-ray counter data (Tm5Sb2Si2—str. type, Cmca—space group, a=14.768(3), b=7.723(2), c=7.741(2) Å, RF=0.0405 for 419 reflections). The Rietveld refinement of the crystal structure of RE5Sb2X2 confirmed the same structure for the RE=Y, Tb, Dy, Ho, Er and Tm and X=Si, Ge. The crystal structure of Tm5Sb2Si2 is an new ordered superstructure of Eu5As4.