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Magnetoelectric antiferromagnets like Cr2O3 are attractive for the realization of energy-efficient and high-speed spin-orbitronic-based memory devices. Here, we demonstrate that fabrication of polycrystalline bulk Cr2O3 samples in conditions far out of equilibrium relying on spark plasma sintering allows to realize high-quality material with density close to that of a single crystal. The sintered sample possesses a preferential [001] texture at the surface, which can be attributed to uniaxial strain applied to the sample during the sintering process. The antiferromagnetic state of the sample and linear magnetoelectric effect are accessed all-electrically relying on the spin Hall magnetoresistance effect in the Pt electrode interfaced with Cr2O3. In line with the integral magnetometry measurements, the magnetotransport characterization reveals that the sample possesses the magnetic phase transition temperature of about 308 K, which is the same as in a single crystal. The antiferromagnetic domain pattern consists of small domains with sizes in the range of several micrometers only, which is formed due to the granular structure of the sample. The possibility to access the magnetoelectric properties of the samples relying on magnetotransport measurements indicates the potential of the polycrystalline Cr2O3 samples for prospective research in antiferromagnetic spintronics.

Soil invertebrates are among the least understood metazoans on Earth. Thus far, the lack of taxonomically broad and dense genomic resources has made it hard to thoroughly investigate their evolution and ecology. With MetaInvert we provide draft genome assemblies for 232 soil invertebrate species, representing 14 common groups and 94 families. We show that this data substantially extends the taxonomic scope of DNA- or RNA-based taxonomic identification. Moreover, we demonstrate that theories of genome evolution cannot be generalised across evolutionarily distinct invertebrate groups. The soil invertebrate genomes presented here will support the management of soil biodiversity through molecular monitoring of community composition and function, and the discovery of evolutionary adaptations to the challenges of soil conditions.

Funding: C.F., U.B. and D.J.R. acknowledge COST Action ‘European Soil-Biology Data Warehouse for Soil Protection’ (EUdaphobase), CA18237, supported by COST (European Cooperation in Science and Technology). AEM thanks the Leverhulme Trust (RPG-2019-401). D.B.B. was supported by an NSF Postdoc Research Fellowship in Biology (NSF 000733206), S.M.R. was supported by an NSERC Discovery Grant Author Contributions, A.V.S. was supported by NSF 1755336, C.S.M was supported by NSF 1398620 and N.J.G was supported by NSF 2019470. 1. Dated, geo-referenced museum specimens are a rich data source for reconstructing species' distribution and abundance patterns. However, museum records are potentially biased towards over-representation of rare species, and it is unclear whether museum records can be used to estimate relative abundance in the field. 2. We assembled 17 coupled field and museum datasets to quantitatively compare relative abundance estimates with the Dirichlet distribution. Collectively, these datasets comprise 73,039 museum records and 1,405,316 field observations of 2,240 species. 3. Although museum records of rare species overestimated relative abundance by 1-fold to over 100-fold (median study = 9.0), the relative abundance of species estimated from museum occurrence records was strongly correlated with relative abundance estimated from standardized field surveys (r2 range of 0.10-0.91, median study = 0.43). 4. These analyses provide a justification for estimating species relative abundance with carefully curated museum occurrence records, which may allow for the detection of temporal or spatial shifts in the rank ordering of common and rare species. Publisher PDF

New clathrate type phases where Li atoms fill vacancies in the Ge-framework have been identified.

Mg

The binary phase Mg3Pt2 was prepared by direct reaction between the elements or by spark-plasma synthesis starting with MgH2 and PtCl2. The compound crystallizes in the monoclinic space group C2/c with a = 7.2096(3) Å, b = 7.1912(4) Å, c = 6.8977(3) Å, and β = 106.072(3)° and is isotypic to Eu3Ga2. Analysis of the electron density within the quantum theory of atoms in molecules shows a significant charge transfer from Mg to Pt in agreement with the electronegativity difference. Further study of the chemical bonding with the electron localizability approach reveals the formation of Pt chains stabilized by a complex system of multicenter interactions involving Mg and Pt species. The metallic character of Mg3Pt2 is confirmed by electronic structure calculations and physical measurements., Mg3Pt2 is a new phase in the Mg−Pt system with a crystal structure built up by anionic Pt chains, which are stabilized by an interplay of multiatomic bonding interactions of Mg with Pt. Mg3Pt2 is a metallic diamagnet.

In a joint effort utilizing modified sample preparation, microscopy, X‐ray diffraction and micro‐fabrication, it became possible to prepare single crystals of the “hidden” phase AlCr2. High‐resolution X‐ray diffraction analysis is described in detail for two crystals with the similar overall composition, but different degree of disorder, which seems to be the main cause for the differing unit cell parameters. Chemical bonding analysis of AlCr2 in comparison to prototypical MoSi2 shows pronounced differences reflecting the interchange of main group element vs. transition metal as majority component., Hidden crystals: With a modified synthesis approach and micro‐fabrication technique, it was possible to isolate micrometer‐sized single crystals of AlCr2 from a largely polycrystalline sample. Chemical bond analysis shows close relation to elements, in contrast to a quite localized bonding pattern in the prototype, MoSi2.

Nanoscale 14(28), 10067 - 10074 (2022). doi:10.1039/D2NR02556F, Band structure engineering has a strong beneficial impact on thermoelectric performance, where theoretical methods dominate the investigation of electronic structures. Here, we use angle-resolved photoemission spectroscopy (ARPES) to analyze the electronic structure and report on the thermoelectric transport properties of half-Heusler TiCoSb high-quality single crystals. High degeneracy of the valence bands at the L and Γ band maximum points was observed, which provides a band-convergence scenario for the thermoelectric performance of TiCoSb. Previous efforts have shown how crystallographic defects play an important role in TiCoSb transport properties, while the intrinsic properties remain elusive. Using hard X-ray photoelectron spectroscopy (HAXPES), we discard the presence of interstitial defects that could induce in-gap states near the valence band in our crystals. Contrary to polycrystalline reports, intrinsic TiCoSb exhibits p-type transport, albeit defects still affect the carrier concentration. In two initially identical p-type TiCoSb crystal batches, distinct metallic and semiconductive behaviors were found owing to defects not noticeable by elemental analysis. A varying Seebeck effective mass is consistent with the change at the Fermi level within this band convergence picture. This report tackles the direct investigation of the electronic structure of TiCoSb and reveals new insights and the strong impact of point defects on the optimization of thermoelectric properties., Published by RSC Publ., Cambridge

The new phase Be

The clathrate-I borosilicide K8−xBySi46−y (0.8 ≤ x ≤ 1.2 and 6.4 ≤ y ≤ 7.2; space group Pmn) was prepared in sealed tantalum ampoules between 900 °C and 1000 °C. By high-pressure preparation at 8 GPa and 1000 °C, a higher boron content is achieved (x = 0.2, y = 7.8). Crystal structure and composition were established from X-ray diffraction data, chemical analysis, WDX spectroscopy, and confirmed by 11B and 29Si NMR, and magnetic susceptibility measurements. The compositions are electron-balanced according to the Zintl rule within one estimated standard deviation. The lattice parameter varies with composition from a = 9.905 A for K7.85(2)B7.8(1)Si38.2(1) to a = 9.968(1) A for K6.80(2)B6.4(5)Si39.6(5).

Pt-based intermetallic compounds M2Pt with anti-CaF2 type of crystal structure and counterpart elements (M) from groups 13 (Al, Ga, In) and 14 (Sn) were studied as electrocatalysts for the oxygen evolution reaction (OER) in acidic media. Polar covalent bonding M–Pt with substantial charge transfer makes the difference between M2Pt and elemental platinum. The compounds M2Pt (M = Al, Ga, In) possess enhanced OER activity compared to elemental Pt and it improves during the partial on-going leaching of the M component. Therefore, the M2Pt compounds act as precursors for formation of OER-active MxPt1−x layers.

N-type Zintl phases with earth-abundant and non-toxic constituent elements have attracted intense research interest thanks to their high thermoelectric efficiencies in the mid-temperature range, exemplified by the recently discovered Mg3Sb2 material. In this study, the liquid phase is expelled from the microstructure of the optimized n-type phase Mg3+xSb1.5Bi0.49Te0.01 by applying a melt-centrifugation technique leading to the formation of lattice dislocations, grain boundary dislocations and increasing porosity. Additional phonon scattering mechanisms were introduced in the microstructure through this manufacturing method, resulting in a significant 50% reduction in the total thermal conductivity from ∼1 W m−1 K−1 to ∼0.5 W m−1 K−1 at 723 K. Combined with high power factors, this reduced heat transport leads to a dimensionless thermoelectric figure of merit, zT, value of ∼1.64 at 723 K, 43% higher than the value obtained in untreated Mg3+xSb1.5Bi0.49Te0.01 (zT ∼ 1.14 at 723 K). This peak zT value yields a predicted device ZT of 0.95, and a promising theoretical thermoelectric efficiency of about 12%. These results further underline the great potential of the lightweight Mg3Sb2 material for mid-temperature energy harvesting via thermoelectric effects.

The ternary compound Hf2B2Ir5 was assessed as an electrocatalyst for the oxygen evolution reaction (OER) in 0.1 M H2SO4 . The oxidative environment restructures the studied material in the near-surface region, creating cavities in which agglomerates of IrOx(OH)y(SO4)z particles are incorporated. These in situ generated particles result from the oxidation of secondary phases in the matrix as well as from self-controlled near-surface oxidation of the ternary compound itself. The oxidation is controlled by the structural and chemical bonding features of Hf2B2Ir5. The cage-like motif, exhibiting mostly ionic interactions between positively charged Hf atoms and a covalently bonded Ir–B network, selectively controls the extent and kinetics of the transformation process induced during the operation of the electrocatalyst. The resulting self-optimized composite material, formed by a Hf2B2Ir5 matrix surrounding IrOx(OH)y(SO4)z particles, was used in the OER over 240 h at 100 mA cm-2 current density. The chemical changes, as well as the OER performance, were studied via a combination of bulk- and surface-sensitive experimental techniques as well as by employing a quantum-chemical bonding analysis.

Zeitschrift für Kristallographie / Crystalline materials 235(8-9), 1-7 (2020). doi:10.1515/zkri-2020-0058, The new samarium germanide SmGe$_3$ is obtained by high-pressure high-temperature synthesis of pre-reacted mixtures of samarium and germanium at a pressure of 9.5 GPa and temperatures between 1073 and 1273 K. SmGe$_3$ decomposes at 470(5) K into SmGe$_2$, $α$-Sm$_3$Ge$_5$ and a hitherto unknown phase. SmGe$_3$ exhibits a superstructure of the cubic Cu$_3$Au-type. Transmission electron microscopy measurements of crystalline particles and prepared lamellae indicate a high density of defects on the nano-scale. Selected area electron diffraction and elaborate X-ray powder diffraction measurements consistently indicate a 2a$_0$×2a$_0$×2a$_0$ superstructure adopting space group $Fm^-3m$ with $a$ = 8.6719(2) Å., Published by ˜Deœ Gruyter, Berlin

The production of hydrogen via water electrolysis is feasible only if effective and stable catalysts for the oxygen evolution reaction (OER) are available. Intermetallic compounds with the well-defined crystal and electronic structures as well as particular chemical bonding features are suggested here to act as precursors for new composite materials with attractive catalytic properties. Al2Pt combines a characteristic inorganic crystal structure (anti-fluorite type) and a strongly polar chemical bonding with the advantage of elemental platinum in terms of stability against dissolution under OER conditions. We describe here the unforeseen performance of a surface nanocomposite architecture resulting from the self-organized transformation of the bulk intermetallic precursor Al2Pt in OER.

Due to promising mechanical and chemical properties, transition metal borides have attracted attention, and numerous studies have investigated various combinations of transition elements in hopes of acquiring a final product with desired properties combined. In this study, novel low-temperature approach was adopted for the synthesis of cobalt-titanium-boron based crystalline powders. The method was based on the single-step direct reaction of CoCl2(s), TiCl4(l) and NaBH4(s) in a sealed reactor under autogenic pressure. After the reaction of the precursors at 850 °C by using the molar ratios of metal chlorides to NaBH4 as 1:3, CoB and TiB2 phases were formed in-situ. The subsequent annealing process at 1100 °C achieved a full conversion of metal chlorides to CoB-TiB2 composite nanostructures. It was concluded that the binary forms of the borides tend to form as separate phases, which is illustrated in the SEM/EDS analyses with different morphologies. Amorphous boron layer surrounded TiB2 particles with an average particle size of 60 nm, whereas the CoB particles formed agglomerates with an average size of 450 nm. The use of synthesized composite powders as reinforcement in metal matrices resulted in enhanced hardness (506 HV) and compressive strength (1682 MPa) of the Ti6Al4V bulk samples.

An efficient application of a material is only possible if we know its physical and chemical properties, which is frequently obstructed by the presence of micro‐ or macroscopic inclusions of secondary phases. While sometimes a sophisticated synthesis route can address this issue, often obtaining pure material is not possible. One example is TaGeIr, which has highly sample‐dependent properties resulting from the presence of several impurity phases, which influence electronic transport in the material. The effect of these minority phases was avoided by manufacturing, with the help of focused‐ion‐beam, a μm‐scale device containing only one phase—TaGeIr. This work provides evidence for intrinsic semiconducting behavior of TaGeIr and serves as an example of selective single‐domain device manufacturing. This approach gives a unique access to the properties of compounds that cannot be synthesized in single‐phase form, sparing costly and time‐consuming synthesis efforts., Perfection not required: In a study of intrinsic properties of intermetallic compounds, the synthesis of either single‐crystal or single‐phase material is the fundamental step. However, some materials cannot be prepared in single‐phase form. A new approach using a micro‐scale amount of material to study its intrinsic properties can significantly shorten this procedure and make the quest for “perfect” samples unnecessary.

The new ternary compound Y4Be33Pt16 was prepared from elements by arc melting, and its crystal structure was determined from single-crystal X-ray diffraction data (space group I4[combining macron]3d, a = 13.4849(3) A). The material is the first representative of a new structure type of complex intermetallic compounds and reveals a cage-like crystal structure. Analysis of chemical bonding by means of the electron localizabilty approach indicates ionic interaction of yttrium with the rest of the crystal structure, characteristic for cage compounds, in particular for clathrates. In contrast to the mostly two-centre bonding in the framework of clathrates, the new compound is characterized by a multi-centre interaction within the framework, caused by the demand of the valence electrons in the system. The non-centrosymmetric material enters the superconducting state at TC = 0.9 K.

Unconventional superconductivity in non-centrosymmetric superconductors has attracted a considerable amount of attention. While several lanthanide-based materials have been reported previously, the number of actinide-based systems remains small. In this work, we present the discovery of a novel cubic complex non-centrosymmetric superconductor $${\text {Th}}_4{\text {Be}}_{{33}}{\text {Pt}}_{{16}}$$ Th 4 Be 33 Pt 16 ($$I{\bar{4}}3d$$ I 4 ¯ 3 d space group). This intermetallic cage compound displays superconductivity below $$T_{\text {c}} = 0.90 \pm 0.04$$ T c = 0.90 ± 0.04 K, as evidenced by specific heat and resistivity data. $${\text {Th}}_4{\text {Be}}_{{33}}{\text {Pt}}_{{16}}$$ Th 4 Be 33 Pt 16 is a type-II superconductor, which has an upper critical field $${\text {H}}_{{\text {c}}2} = 0.27$$ H c 2 = 0.27 T and a moderate Sommerfeld coefficient $$\gamma _{\text {n}} = 16.3 \pm 0.8$$ γ n = 16.3 ± 0.8 mJ $${\text {mol}}^{-1}_{\text {Th}}$$ mol Th - 1 $${\text {K}}^{-2}$$ K - 2 . A non-zero density of states at the Fermi level is evident from metallic behavior in the normal state, as well as from electronic band structure calculations. The isostructural $${\text {U}}_4{\text {Be}}_{{33}}{\text {Pt}}_{{16}}$$ U 4 Be 33 Pt 16 compound is a paramagnet with a moderately enhanced electronic mass, as indicated by the electronic specific heat coefficient $$\gamma _{\text {n}} = 200$$ γ n = 200 mJ $${\text {mol}}^{-1}_{\text {U}}$$ mol U - 1 $${\text {K}}^{-2}$$ K - 2 and Kadowaki–Woods ratio $$A/\gamma ^2 = 1.1 \times 10^{-5}$$ A / γ 2 = 1.1 × 10 - 5 $$\upmu $$ μ $$\Omega $$ Ω cm $${\text {K}}^2$$ K 2 $${\text {mol}}_{\text {U}}^2$$ mol U 2 (mJ)$$^{-2}$$ - 2 . Both $${\text {Th}}_4{\text {Be}}_{{33}}{\text {Pt}}_{{16}}$$ Th 4 Be 33 Pt 16 and $${\text {U}}_4{\text {Be}}_{{33}}{\text {Pt}}_{{16}}$$ U 4 Be 33 Pt 16 are crystallographically complex, each hosting 212 atoms per unit cell.