Abstract
Crystals of NaPd$_3$Ge$_2$, (X = Si, Ge, Sn) were synthesized and their crystal structures investigated by single crystal X-ray diffraction. The previously reported structures of NaPd$_3$Si$_2$ and NaPd$_3$Sn$_2$ were confirmed. NaPd$_3$Ge$_2$ was found to have a different unit cell from that originally reported; therefore the structure was solved. It is an orthorhombically distorted version of the hexagonal CeCo$_3$Be$_2$-type structure, in space group Imma, with cell parameters a = 7.244(1) Å, b = 9.938(1) Å, c = 5.767(2) Å. The originally reported cell is explained through triple twinning of the true cell. The structure of NaPd$_3$Ge$_2$ fits the trend of decreasing X–X dimerization as a function of increasing period from Si–Sn. All three compounds are metals showing weak diamagnetism with increasing resistivity from NaPd$_3$Si$_2$–NaPd$_3$Sn$_2$; no superconductivity is observed down to 2 K.
Ali, Mazhar N