Search

The intermetallic phases Yb11Bi10-xSnx (x = 0, 4.8) are prepared by solid state reaction of stoichiometric mixtures of the elements (Ta ampules in evacuated silica ampules, 1.

Die Tetraarsenidometallate(V) M7[TAs4] (M = K, Rb; T = Nb, Ta) wurden aus RbAs, KAs, Rb3As, K3As und elementarem Nb bzw. Ta in geschlossenen Nb(Ta)-Ampullen bei 1100 K dargestellt. Sie kristallisieren in einem neuen Strukturtyp oP24 (Pmn21, Nr. 31); K7[NbAs4]: a = 1019.2(2) pm, b = 916.2(2) pm, c = 830.6(1) pm; K7[TaAs4]: a = 1017.3(2) pm, b = 915.5(2) pm, c = 830.5(2) pm; Rb7[NbAs4]: a = 1059.2(4) pm, b = 952.8(4) pm, c = 860.4(4) pm; Z = 2 Formeleinheiten). Die luft- und hydrolyseempfindlichen Verbindungen bilden dunkelrote, quaderformige Kristalle. Sie sind Halbleiter mit Eg = 1.80 eV. Der thermische Abbau im dynamischen Vakuum liefert Hinweise auf die Existenz von K4TAs3 und K2TAs2 (T = Nb, Ta). Wesentliche Baueinheiten sind polar ausgerichtete [TAs4]-Tetraeder mit d (T – As) = 252.2(1) pm, 251.3(1) pm bzw. 253.0(4) pm. Die As-Atome sind trigonal-prismatisch von M- und T-Atomen umgeben. Diese trigonalen Prismen bilden entlang der b-Achse abwechselnd anionische und kationische Schichten, [M4As2]2− bzw. [M3TAs2]2+. Die Strukturen sind mit der von Co2P vergleichbar und konnen als aufgefullte Schervarianten der Na6□ZnO4-Struktur aufgefast werden. Synthesis, Structure, and Properties of the Tetraarsenidometallates(V) M7[TAs4] (M = K, Rb; T = Nb, Ta) The tetraarsenidometallates(V) M7[TAs4] (M = K, Rb; T = Nb, Ta) have been prepared from RbAs, KAs, Rb3As, K3As, and Nb or Ta in sealed Nb(Ta) ampoules at T = 1100 K. They crystallize in a new structure type oP24 (Pmn21, no. 31); K7[NbAs4]: a = 1019.2(2) pm, b = 916.2(2) pm, c = 830.6(1) pm; K7[TaAs4]: a = 1017.3(2) pm, b = 915.5(2) pm, c = 830.5(2) pm; Rb7[NbAs4]: a = 1059.2(4) pm, b = 952.8(4) pm, c = 860.4(4) pm; Z = 2 formula units per unit cell). The compounds form dark red crystals and they are sensitive against air and moisture. They are semiconductors with Eg = 1.80 eV. The thermal decomposition in dynamical vacuum gives evidence for the existance of K4TAs3 and K2TAs2 (T = Nb, Ta). Main structural units are polar oriented tetrahedra [TAs4] with d(T – As) = 252.2(1) pm; 251.3(1) pm; 253.0(4) pm, respectively. The As atoms are trigonal prismatically coordinated by M and T atoms. These trigonal prisms form anionic and cationic layers [M4As2]2− and ∞2[M3TAs2]2+ alternating along the b axis. The structure is comparable with that of Co2P and can be described as a stuffed shear variant of the Na6□ZnO4 type of structure.

Das neuartige Arsenid KLi2As wurde aus den Elementen bzw. aus Mischungen der binaren Komponenten Li3As und K3As in zugeschweisten Niobampullen bei 823 K bzw. 623 K dargestellt. Es kristallisiert in der Raumgruppe Pmmn (Nr. 59) mit a = 445.8(9); b = 671.5(11); c = 627.0(12) pm und Z = 2 Formeleinheiten. Die metallisch glanzenden silberfarbenen Plattchen hydrolysieren schnell an feuchter Luft. Die Verbindung (Pearson-Code oP8) ist isopuntal zu BaLi2Si und ein Zwischenglied zwischen der Li3N- und der Na3As-Struktur. Kalium ist verzerrt tetraedrisch von vier As-Atomen (d(KAs) = 355 und 367 pm), Arsen von vier Kalium- und sechs Lithiumatomen (d(AsK) = 355–367 pm; d(AsLi) = 260–265 pm) in Form eines Sphenocorona koordiniert. Lithium ist verzerrt trigonal-planar von Arsen koordiniert, umhullt von einem einfach uberdachten trigonalen Prisma aus drei Lithium und vier Kaliumatomen. Preparation, Crystal Structure, and Properties of KLi2As The novel arsenide KLi2As has been synthesized either from the elements or from mixtures of the binary components Li3As and K3As in sealed Nb ampoules at 823 K and 623 K, respectively. It crystallizes in the space group Pmmn (no. 59) with a = 445.8(9); b = 671.5(11); c = 627.0(12) pm and Z = 2 formula units. The metallic reflecting silvercoloured platelets hydrolize rapidly under wet air. The compound (Pearson code oP8) is isopuntal with BaLi2Si and an intermediate between the Li3N and the Na3As type of structure. Potassium is distorted tetrahedrally coordinated by four As atoms (d(KAs) = 355 and 367 pm), arsenic by four potassium and six lithium atoms (d(AsK) = 355–367 pm; d(AsLi) = 260–265 pm) in form of a sphenocorona. Lithium is threefold coordinated (distorted trigonal planar) by arsenic and this unit is enveloped by a monocapped trigonal prism build by three lithium and four potassium atoms.

Die neuartigen Verbindungen Na16(ARb6)Sb7 wurden aus den entsprechenden Elementen in verschweisten Nb-Ampullen bei 873 K (A = Rb) bzw. 823 K (A = I, Na, Au) dargestellt. Sie bilden sprode silberfarbene Kuboktaeder (A = Rb) bzw. unregelmasige Polyeder (silberglanzend: A = Na, I; metallisch golden glanzend: A = Au). Die Verbindungen zersetzen sich schnell an feuchter Luft zu grauen Produkten. Die Kristallstrukturen wurden an Einkristallen bestimmt (A = Rb: a = 1565,8(2) pm; A = I: a = 1563,3(2) pm; A = Na: a = 1562,6(2) pm; A = Au: a = 1560,7(2) pm). Sie kristallisieren in der Raumgruppe Fm3m (Nr. 225) mit Z = 4 Formeleinheiten und sind isotyp zu Sc11Ir4. Die Verbindungen sind Zintl-Phasen, deren Strukturen als achtfache Defektvariante der Li3Bi-Struktur (cF128-8; a = 2a′ (Li3Bi)) beschrieben werden konnen. Die Sb-Atome bilden ein Netz von Kuboktaedern, die abwechselnd durch SbNa8-Wurfel bzw. durch ARb6-Oktaeder zentriert werden. Wesentliches Strukturmerkmal sind die A−-Anionen im Rb6-Oktaeder, deren Existenz durch die Darstellung der isotypen Verbindungen mit typischen Anionenbildnern (A = Au, I), durch elektrostatische Betrachtungen und Berechnungen der Volumeninkremente manifestiert wird. Im Einklang mit den nach dem Zintl-Konzept zu erwartenden elektronischen Eigenschaften ist Na16(RbRb6)Sb7 ein diamagnetischer Halbleiter mit Eg = 0,33 eV und χmol = −508 × 10−6 cm3 mol−1. The Cubic Phases Na16(ARb6)Sb7, Compounds with the Anions A = Rb−, Na−, Au−, I− The novel compounds Na16(ARb6)Sb7 have been synthesized from the elements in sealed Nb ampoules at 873 K (A = Rb) and 823 K (A = I, Na, Au). They form brittle cuboctahedra (silver metallic; A = Rb) and irregular polyhedra (silver metallic lustre; A = Na, I; golden metallic lustre; A = Au). They rapidly decompose in moist air to gray products. Their crystal structures have been determined by single crystal X-ray crystallography (A = Rb: a = 1565.8(2) pm; A = I: a = 1563.3(2) pm; A = Na: a = 1562.6(2) pm; A = Au: a = 1560.7(2) pm). They crystallize cubically in the space group Fm3m (no. 225) with Z = 4 formula units and are isotypic with Sc11Ir4. The compounds are ZINTL phases and their structures can be described as an eightfold defect variant of the Li3Bi type of structure (cF128-8; a = 2a′(Li3Bi)). The Sb atoms form a network of cuboctahedra, centered alternatingly by a SbNa8 cube or a ARb6 octahedron. Main structural features are the anions A− within the Rb6 octahedron. Supporting the existence of A− are the isotypical compounds with the more common anion forming elements (A = Au, I), as well as electrostatic potential considerations together with calculations of the volume increments. The semiconducting properties (Eg = 0.33 eV) of Na16(RbRb6)Sb7, as well as the diamagnetism χmol = −508 × 10−6 cm3 mol−1, are in accordance with those to be expected from the Zintl concept.

The title compounds are prepared by thermal decomposition of the metastable phases LnGe5 (obtained by arc-melting of the elements at 923—1123 K and 8.3—9.5 GPa) at 543—573 K and ambient pressure for 2 h.

YbRh2Si2 has advanced to a prototype material for investigating physics related to the Kondo effect. An optimization of the synthesis resulted in single crystals of extraordinary crystalline quality. At the atomic scale, we utilize scanning tunneling microscopy to study the topography of cleaved single crystals. A structural and chemical analysis was conducted by highly accurate x-ray diffraction and wavelength dispersive x-ray spectroscopy measurements. The latter indicate a homogeneity range of the YbRh2Si2 phase between approximately 40.0–40.2 at.% Rh. For our high-quality samples the number of defects found on the atomic scale (of the order of 0.3% of the visible lattice sites) is in quantitative agreement with a very small off-stoichiometry within this homogeneity range. Comparing our results for these samples allows an assignment of the structural defects observed at the cleaved surfaces to Rh occupying Si sites and, even less numerous Si in Rh sites. Such an analysis is hampered for samples of lesser quality, but there seem to be numerous empty Si-sites. Based on these observations the results of scanning tunneling spectroscopy can be analyzed in further detail and provide insight into the Kondo physics.

picture behind the measured phenomenon. We show in detail that the electronic structure of the substitution variants of the intermetallic system RuIn3−xAx (A = Sn, Zn) changes in a rigid-band-like fashion. This behavior makes possible the fine tuning of the substitution concentration to take advantage of the sharp peaklike features in the density of states of the semiconducting parent compound. Trends in the transport properties calculated using the semiclassical Boltzmann transport equations within the constant scattering time approximation are in good agreement with the former experimental results for RuIn3−xSnx. Based on the calculated thermopower for the p-doped systems, we reinvestigated the Zn-substituted derivative and obtained ZnO-free RuIn3−xZnx .T he new experimental results are consistent with the calculated trend in thermopower and yield a large zT value of 0.8.

Mestrado em Ensino da Educação Física nos Ensinos Básico e Secundário O Estágio Pedagógico desenvolvido na Escola Básica Integrada Rainha D. Leonor de Lencastre, localizada em S. Marcos, concelho de Sintra, teve em vista o culminar da formação inicial para a função docente. O presente relatório está inserido no 2º ano do 2º ciclo de estudos conducente ao grau de Mestre em Ensino da educação Física nos Ensinos Básico e Secundário, da Faculdade de Motricidade Humana, e visa documentar todo o processo formativo que decorreu durante este ano lectivo. O guia de Estágio Pedagógico 2011/2012 foi a grande referência onde se encontram especificados os objetivos a atingir nas quatro áreas de formação: Organização e Gestão do Ensino e da Aprendizagem (Área 1), Inovação e Investigação Pedagógica (Área 2), Participação na Escola (Área 3) e Relação com a comunidade (Área 4). Em relação a cada uma destas áreas será realizada uma aprofundada descrição, reflexão e análise sobre os principais aspetos, decisões, estratégias, intervenções e resultados que enriqueceram este período de formação profissional supervisionado. Será ainda realizada uma reflexão crítica global sobre todo o processo de formação, com especial incidência nos aspetos mais relevantes deste estágio pedagógico.

The title compounds are prepared by high temperature/high pressure reactions of mixtures of the elements in the molar ratio RE:B:S = 1:3:6 (3.5 GPa, 1673 K, 5 h).

Structural, magnetic, and powder and single-crystal electron paramagnetic resonance (EPR) studies were performed on [{Cu(bipy)(en)}{Cu(bipy)(H(2)O)}{VO(3)}(4)](n) (bipy = 2,2'-bipyridine, en = ethylenediamine), which is a new copper-vanadium hybrid organic-inorganic compound containing Cu(II) and V(V) centers. The oxovanadium units provide an anionic scaffolding to the structure, where two types of Cu(II) coordination modes, octahedral (Cu1) and square pyramidal (Cu2), contribute to the magnetic properties. The crystal structure contains layers including Cu1 and Cu2 ions, separated by stacked arrangements of 2,2'-bipyridine molecules. Each type of Cu(II) ion in these layers forms parallel spin chains described by exchange coupling parameters J(1) and J(2) for Cu1 and Cu2, respectively (exchange couplings defined as H(ex)(i,j) = -J(ij)S(i)S(j)), which, for necessity, are assumed to be equal to J. These chains are coupled by much weaker Cu1-Cu2 exchange interactions J(3) connecting neighbor Cu1 and Cu2 ions within a layer, through paths acting as rungs of a ladder chain structure. The average coupling J, which is antiferromagnetic (J0), according to the susceptibility data, is estimated with similar results with a mean field approximation (J = -1.4 cm(-1)), and with a uniform chain model (J = -1.7 cm(-1)). The EPR spectra of powdered samples and oriented single crystals are shown to be independent of J(1) and J(2), but are dependent on the weak coupling J(3), and the data allow a lower limit to be established: |J(3)|0.04 cm(-1). The spectra are also strongly sensitive to extremely weak coupling interactions with average magnitude J(4) between copper atoms in neighboring layers, separated by ∼10 Å, using the stacked 2,2'-bipyridine molecules, which produce a 2D-to-3D quantum phase transition. This is observed in single-crystal samples when the energy levels are changed with the orientation of the magnetic field. From the characteristics of these transitions, we estimate a value of |J(4)| = 0.0034 ± 0.0004 cm(-1) between Cu(II) ions in neighboring layers. This work emphasizes the important possibilities of EPR to evaluate extremely small exchange couplings between metal ions in a solid material, even in the presence of other much larger couplings.

The intercalation of the cationic binuclear macrocyclic complex [Zn 2 L] 2+ (LH 2 : macrocyclic ligand obtained by the template condensation of 2-hydroxy-5-methyl-1,3-benzenedicarbaldehyde and 1,2-diaminobenzene) was achieved by a cationic exchange process, using K 0.4 Mn 0.8 PS 3 as a precursor. Three intercalated materials were obtained and characterized: (Zn 2 L) 0.05 K 0.3 Mn 0.8 PS 3 (1) , (Zn 2 L) 0.1 K 0.2 Mn 0.8 PS 3 (2) and (Zn 2 L) 0.05 K 0.3 Mn 0.8 PS 3 (3) , the latter phase being obtained by an assisted microwave radiation process. The magnetic data permit to estimate the Weiss temperature θ of ≈−130 K for (1) ; ≈−155 K for (2) and ≈−130 K for (3) . The spin canting present in the potassium precursor remains unperturbed in composite (3) , and spontaneous magnetization is observed under 50 K in both materials. However composites (1) and (2) do not present this spontaneous magnetization at low temperatures. The electronic properties of the intercalates do not appear to be significantly altered. The reflectance spectra of the intercalated phases (1) , (2) and (3) show a gap value between 1.90 and 1.80 eV, lower than the value observed for the K 0.4 Mn 0.8 PS 3 precursor of 2.8 eV.

The corrosion of thermoelectric clathrates alpha- and beta-Eu8Ga16-xGe30+x is studied under static air (DSC/TG) up to 650 °C. Oxidation product layers with thicknesses of 10.5 µm (alpha-Eu8Ga16-xGe30+x) and 4.5 µm (beta-Eu8Ga16-xGe30+x) are formed. The oxidation begins at 360 and 380 °C, respectively. XRD pattern of the beta-Eu8Ga16-xGe30+x oxidized layer shows Ge and four Eu2O3 reflections; while alpha-Eu8Ga16-xGe30+x data (sample crushed and grinded) shows alpha-Eu8Ga16-xGe30+x reflections (majority phase), two EuGa2±xGe4minus-or-plus signx strongest reflections and Ge (minority phases). These results indicate the amount of oxides is very small or they are amorphous. High temperature powder XRD measurements on alpha-Eu8Ga16-xGe30+x under air confirm the oxidation onset temperature determined in DSC studies.

The high-temperature, high-pressure syntheses of hp-LnSn3-x (Ln: Tb, Ho, Er) are reinvestigated.

The new compound TbGe5 is obtained from a stoichiometric mixture of Tb and Ge under high-pressure, high-temperature conditions (8.3 GPa, 820 K, 9 h).

The title compound Na-2[BH4][NH2] Na2BNH6 exists in two different modifications: the low-temperature (LT) beta- and the high-temperature (HT) alpha-phase. The HT alpha-Na2BNH6 is accessible by single heating of the binaries NaNH2 and NaBH4 (molar ratio = 1:1) to the melting point of 492 K for I h in evacuated Pyrex ampoules. On longer annealing (T = 342 K, 10 days), the HT alpha-phase converts completely to the LT beta-phase. The beta -> alpha transition at 371 K is very fast, but the conversion alpha -> beta is quite slow. No further phase formation was detected in the system up to a molar ratio of 5:1 (NaNH2:NaBH4). The cubic alpha-Na2BNH6 crystallizes in the K3SO4F-type of structure (space group: Pm (3) over barm, Z = 1) with a = 4.6950(1) angstrom. beta-Na2BNH6 crystallizes in orthorhombic symmetry (space group: Pbcm, Z = 4) with a = 6.5384(2) angstrom. b = 6.4960(1) angstrom, c=9.8512(2)angstrom. Both structures can directly be derived from the perovskite type structure ABO(3), with the [BH4](-) and [NH2](-) moieties in the A and B sites, respectively. The charge balancing Na ions are occupying 2/3 of the O positions. In both cases, the presence of the two different anions in the solids was also confirmed by vibrational spectra. According to DTA and high temperature X-ray diffraction (HT-XRD) measurements, the educts NaNH2 and NaBH4 react at 430 K to form alpha-Na2BNH6 which remains stable until the melting point of 492 K. Between 492 and 573 K, no significant effects were detected in DTA and TG. Above 573 K, however, a sudden decomposition takes place in two steps (659 and 689 K) causing a total mass loss of 8%. The gaseous species formed during the decomposition process were followed by mass spectra (MS). The mass spectra obtained from 1:1 and 2:1 mixtures of NaNH2 and NaBH4 in the range 492 K < T < 773 K prove that the main gaseous product evolved during the thermal decomposition is H-2. NH3 and H2O were also detected, but their concentrations are quite low. These findings confirm that the mixture of the complex hydrides NaNH2-NaBH4 (molar ratio >= 1:1) - comparable to the LiNH2-LiBH4 system - are potential candidates for solid hydrogen storage materials. The composition of the solid residues after the thermal treatment depends on the molar ratio of the starting binaries NaNH2 and NaBH4. While Na2BNH6 (1:1) decomposes to a mixture of NaH, Na and an unidentified amorphous solid, mixtures >= 2:1 yielded exclusively Na3BN2.

The isostructural compounds EuTM2Ga8 (TM = Co, Rh, Ir) were prepared by direct reaction of the elements by high-frequency thermal treatment. All three phases are isotypic with CeFe2Al8 (space group...

The magnetic properties and electronic structure of thulium diboride were investigated as it is a magnetically unknown phase between ferromagnetic (FM) $RE{\text{B}}_{2}$ $(RE=\text{Tb},\text{Dy},\text{Ho},\text{Er})$ and antiferromagnetic ${\text{YbB}}_{2}$. ${\text{TmB}}_{2}$ adopts the ${\text{AlB}}_{2}$-type crystal structure $(P6/mmm)$ with $a=3.26016(5)\text{ }\text{\AA{}}$ and $c=3.75351(8)\text{ }\text{\AA{}}$ and exhibits long-range FM order with the specific heat ${C}_{p}$ exhibiting a peak at ${T}_{C}=7.2\text{ }\text{K}$ at the Curie temperature. A Curie-Weiss fit of the magnetic susceptibility yielded ${\ensuremath{\mu}}_{\text{eff}}=7.49{\ensuremath{\mu}}_{B}/\text{Tm}$ $({\text{Tm}}^{3+})$ and weak FM interactions. A Schottky anomaly in ${C}_{p}$ was used to investigate crystal electric field (CEF) effects. From a measurement of ${C}_{p}(T)$ of the isostructural ${\text{LuB}}_{2}$ the magnetic entropy ${S}_{\text{mag}}$ of ${\text{TmB}}_{2}$ is determined. The ordered state of the Tm ions involves three CEF levels. Electronic-structure calculations, performed within the local spin density approximation, indicate a Ruderman-Kittel-Kasuya-Yoshida-type mechanism for the magnetic order. With respect to the total energy, ferromagnetic order is found to be more stable than the $A$-type antiferromagnetically ordered state, in agreement with the experiment.

The magnetic susceptibility, field-dependent heat capacity, and electrical transport properties (resistivity and Hall effect) are investigated for filled skutterudites $M{\mathrm{Fe}}_{4}{\mathrm{Sb}}_{12}$ with $M=\mathrm{Na}$, K, Ca, Sr, Ba, Yb, and La. The specific heat ${c}_{p}(T)$ reveals linear terms $\ensuremath{\gamma}$ ranging from $100\phantom{\rule{0.3em}{0ex}}\text{to}\phantom{\rule{0.3em}{0ex}}200\phantom{\rule{0.3em}{0ex}}\mathrm{mJ}\phantom{\rule{0.2em}{0ex}}{\mathrm{mol}}^{\ensuremath{-}1}\phantom{\rule{0.2em}{0ex}}{\mathrm{K}}^{\ensuremath{-}2}$. An Einstein term contributing to ${c}_{p}(T)$ is analyzed and discussed in connection with thermal vibrations of the cations $M$. The Einstein temperatures ${\ensuremath{\Theta}}_{E}=70--105\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ are compared with values derived from atomic displacement parameters obtained by x-ray diffraction and other methods. Deviations of the amplitude and frequency of the Einstein term from the expected values are discussed. The paramagnetic susceptibility and the magnetic ground state varies systematically with the cation charge. While $\mathrm{Na}{\mathrm{Fe}}_{4}{\mathrm{Sb}}_{12}$ and $\mathrm{K}{\mathrm{Fe}}_{4}{\mathrm{Sb}}_{12}$ are nearly half-metallic weak itinerant ferromagnets with ${T}_{C}\ensuremath{\approx}80\phantom{\rule{0.3em}{0ex}}\mathrm{K}$, $\mathrm{Ca}{\mathrm{Fe}}_{4}{\mathrm{Sb}}_{12}$, $\mathrm{Sr}{\mathrm{Fe}}_{4}{\mathrm{Sb}}_{12}$, $\mathrm{Ba}{\mathrm{Fe}}_{4}{\mathrm{Sb}}_{12}$, and $\mathrm{Yb}{\mathrm{Fe}}_{4}{\mathrm{Sb}}_{12}$ are nearly ferromagnetic metals with a high Sommerfeld-Wilson ratio and strong ferromagnetic spin fluctuations. $\mathrm{La}{\mathrm{Fe}}_{4}{\mathrm{Sb}}_{12}$ is paramagnetic with predominantly antiferromagnetic fluctuations. The decrease of the low-temperature specific heat with magnetic field is investigated. A large positive magnetoresistance is observed for both ferromagnetic and nearly ferromagnetic compounds, while that of the La compound is small. Size and temperature dependence of the Hall coefficient points to a compensation of hole and electron carriers. The temperature dependence of the resistivity displays different characteristic power laws and an anomaly around $80\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. These observations can be explained by details of the electronic structure. A systematic variation of the properties with charge transfer from the cation $M$ to the $[{\mathrm{Fe}}_{4}{\mathrm{Sb}}_{12}]$ polyanion is recognized.

Monoaquatris(tetraoxorhenate (VII)) bismuth(III), Bi(ReO 4 ) 3 (H 2 O) was prepared by reaction of (BiO) 2 CO 3 /Bi 2 (CO 3 ) 3 with concentrated HReO 4 at room temperature. The pale yellow compound crystallize triclinic in the space group P1;, (No. 2); with two formula units per unit cell (a = 746.0(1) pm, b = 777.1(2) pm, c = 990.5(2) pm, α = 100.99(3)°, β = 99.88(3)°, γ = 100.17(3)° ). The main feature of the crystal structure is a distorted bicapped trigonal prism of Bi[(ReO 4 ) 3/2 (ReO 4 ) 2/2 (ReO 4 ) 2/2 (H 2 O)], which are connected each other through [ReO 4 ]-tetrahedra to form a three-dimensional network. In the titled compound, the cation Bi 3+ is eightfold coordinated which agree with the tendency observed in other compounds of the family. Keywords: crystal structure, perrhenate anions, X-ray diffraction, coordination number INTRODUCTION In previous publications we reported the synthesis and crystal structure of tetraoxorhenates (VII) of some rare earth metals like Gd, Sm, Eu, Yb, La

Structural, thermal, electronic, and electrical transport properties as well as high-field $^{57}\mathrm{Fe}$ M\"ossbauer investigations are reported for thallium iron antimonide $\mathrm{Tl}{\mathrm{Fe}}_{4}{\mathrm{Sb}}_{12}$, in which thallium attains the formal charge of $+1$. Similar to the isostructural $\mathrm{Na}{\mathrm{Fe}}_{4}{\mathrm{Sb}}_{12}$ and $\mathrm{K}{\mathrm{Fe}}_{4}{\mathrm{Sb}}_{12}$ homologues, the Tl-filled skutterudite is an itinerant ferromagnet with small ordered moment below ${T}_{C}=80\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. The electronic structure calculated by density functional methods exhibits a band-ferromagnetic ground state and nearly half-metallic properties. The specific heat is dominated by a low-lying mode due to vibrations of the Tl cation in the cavity of the $[{\mathrm{Fe}}_{4}{\mathrm{Sb}}_{12}]$ polyanionic host. Electrical resistivity displays a characteristic hump and a sharp anomaly at ${T}_{C}$. These features and the large magnetoresistance at low temperatures can be explained by a strong compensation of hole and electron carriers in the band structure. Temperature-dependent $^{57}\mathrm{Fe}$ M\"ossbauer spectroscopy confirms the magnetic character.

The binary compound Yb5Bi3 was synthesized by reaction of the elements in a sealed Ta container. Its crystal structure was determined from single-crystal X-ray diffraction data: β -Yb5Sb3-type, space group Pnma, Pearson code oP32, a = 12.6375(6), b = 9.7243(4), c = 8.4117(5) A,V = 1033.72(9) A3, Z = 4, Rgt(F) = 0.028, wRref(F) = 0.069, T = 290 K. Band structure calculations and analysis of the chemical bonding suggest mainly ionic interactions in the crystal structure and a possible presence of ytterbium in two valence states Yb2+ and Yb3+. The magnetization measurements showed that at low temperatures Yb5Bi3 contains ytterbium exclusively in the 4 f 14 configuration without fluctuations to the Yb 4 f 13 configuration up to 400 K. From the Yb-LIII X-ray absorption spectroscopy data the effective valence of ytterbium was found to be 2.11 (89% of Yb in 4 f 14 configuration).