The new stannide ScAgSn was synthesized by induction melting of the elements in a sealed tantalum tube andsubsequent annealing. ScAgSn crystallizes with a pronounced subcell structure: ZrNiAl type,
P![](/images/entities/sixmacr.gif)
2
m,
a = 708.2(2)pm,
c = 433.9(1) pm, wR2 = 0.1264, 321
F2 values, and 14 variables. The Guinier powder pattern reveals weaksuperstructure reflections pointing to a TiFeSi-type structural arrangement:
I2
cm,
a = 708.1(1) pm,
b = 1225.2(2)pm,
c = 869.9(1) pm, wR2 = 0.0787, 5556
F2 values, and 49 variables. So far the growth of high-quality singlecrystals failed. Determination of the superstructure was partly based on merohedral triplet X-ray data augmentedby
119Sn Mössbauer spectroscopy and
119Sn and
45Sc solid-state NMR data. In particular, the observation of threecrystallographically inequivalent sites in
45Sc NMR triple quantum magic-angle spinning (TQ-MAS) NMR spectraprovided unambiguous proof of the superstructure proposed. The ScAgSn structure consists of a three-dimensional[AgSn] network (with Ag-Sn distances between 273 and 280 pm) in which the scandium atoms are located indistorted hexagonal channels, each having five tin and two silver nearest neighbors. Both crystallographicallyindependent tin sites have a tricapped trigonal prismatic coordination, that is, [Sn1Sc
6Ag
3] and [Sn2Ag
6Sc
3]environments, which are well distinguished in the
119Sn NMR and Mössbauer spectra because of their different sitesymmetries.