The synthesis and a joint experimental and theoretical study of the crystal structure and physical properties of the new ternary intermetallic compound TiGePt are presented. Upon heating, TiGePt exhibits an unusual structural phase transition with a huge volume contraction of about 10 %. The transformation is characterized by a strong change in the physical properties, in particular, by an insulator–metal transition. At temperatures below 885 °C TiGePt crystallizes in the cubic MgAgAs (half‐Heusler) type (LT phase, space group F$\bar 4$3m, a=5.9349(2) Å). At elevated temperatures, the crystal structure of TiGePt transforms into the TiNiSi structure type (HT phase, space group Pnma, a=6.38134(9) Å, b=3.89081(5) Å, c=7.5034(1) Å). The reversible, temperature‐dependent structural transition was investigated by in‐situ neutron powder diffraction and dilatometry measurements. The insulator–metal transition, indicated by resistivity measurements, is in accord with band structure calculations yielding a gap of about 0.9 eV for the LT phase and a metallic HT phase. Detailed analysis of the chemical bonding in both modifications revealed an essential change of the Ti–Pt and Ti–Ge interactions as the origin of the dramatic changes in the physical properties.

The X-ray single-crystal diffraction intensities of the intermetallic compound TiGePt were analysed. These showed beyond doubt that the crystal structure is non-centrosymmetric. The analysis revolves around the resonant-scattering contribution to differences in intensity between Friedel opposites hkl and . The following techniques were used: Rmerge factors on the average (A) and difference (D) Author(s) of this paper may load this reprint on their own web site or institutional repository provided that this cover page is retained. Republication of this article or its storage in electronic databases other than as specified above is not permitted without prior permission in writing from the IUCr. Acta Crystallographica Section B: Structural Science, Crystal Engineering and Materials publishes scientific articles related to the structural science of compounds and materials in the widest sense. Knowledge of the arrangements of atoms, including their temporal variations and dependencies on temperature and pressure, is often the key to understanding physical and chemical phenomena and is crucial for the design of new materials and supramolecular devices. Acta Crystallographica B is the forum for the publication of such contributions. Scientific developments based on experimental studies as well as those based on theoretical approaches, including crystal-structure prediction, structureproperty relations and the use of databases of crystal structures, are published.Crystallography Journals Online is available from journals.iucr.org Acta Cryst. (2013 The X-ray single-crystal diffraction intensities of the intermetallic compound TiGePt were analysed. These showed beyond doubt that the crystal structure is non-centrosymmetric. The analysis revolves around the resonant-scattering contribution to differences in intensity between Friedel opposites hkl and h h k k l l. . This result is probably due to the fact that the resonant scattering of Pt is larger for Mo K than for AgK radiation.

We present a combined experimental and theoretical study of the electronic structure of the intermetallic compound TiGePt by means of photoelectron spectroscopy, x-ray absorption spectroscopy and full potential band structure calculations. It was recently shown [Ref. 1] that TiGePt undergoes a structural phase transition by heating which is accompanied by a large volume contraction and a drastic change of physical properties, in particular a large decrease of the electrical resistivity. The present study revealed substantial differences in the electronic structure for the two TiGePt modifications, although they have the same nominal composition and show similar electron counts for particular valence band states. Our photoemission experiments and band structure calculations establish that an insulator-to-metal transition occurs with an appreciable band broadening and closing of the band gap.

- Abstract The new ternary compound NbGePt was prepared by direct reaction of the elements. The crystal structure was investigated by single-crystal X-ray diffraction methods: structure type TiNiSi, Pearson symbol oP 12, space group Pnma , a = 6.4487(3) Å, b = 3.9300(2) Å, c = 7.5065(4) Å, Z = 4. Analysis of chemical bonding by the electron density/electron localizability approach revealed, beside the expected Ge–Pt bonds, strong covalent interactions between Nb and Ge. Graphical abstrac