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Abstract: Magnetic and thermoelectric properties of the skutterudites AT4Sb12 filled with non-magnetic atoms, A=Ca, Sr, Ba and La, are found to depend strongly on the transition-metal elements, T=Fe, Ru and Os. The strong spin fluctuations in the Fe-based compounds manifest themselves as an enhanced specific-heat coefficient γ=100mJ/K2 mol. The maximum of the magnetic susceptibility at 50K observed for A=Ca, Sr and Ba is a characteristic of a nearly ferromagnetic system. The increase of the paramagnetic Curie temperature from 3 to 54K on going from A=La, Ba, Sr to Ca indicates the enhancement of ferromagnetic interactions in the Fe 3d narrow band. Except for A=La, a marked shoulder appears in the thermopower at 50K which is totally suppressed by the application of a magnetic field of 14T. The Ru compounds are metallic diamagnets with γ=10mJ/K2 mol, while the Os compounds are strongly enhanced Pauli paramagnets with γ=45mJ/K2 mol and show behaviors of a strongly coupled electron–phonon system. The lattice thermal conductivity for either A=La or T=Os does not show a peak near 50K and its value is much smaller than other compounds. The strong phonon scattering can be caused by rattling of the relatively small La3+ ion in the T4Sb12 cage or tunneling of Sr2+ and Ba2+ ions in the Os4Sb12 cage. [Copyright &y& Elsevier]

We report a systematic study of thermoelectric properties of a series of Ce-based compounds with the ϵ-TiNiSi-type structure; metallic CePtSn, semimetallic CeNiSn and CeRhSb, and semiconducting CeRhAs. In this sequence, both the Kondo temperature and hybridization-gap width increase, whereas the phonon thermal conductivity at high temperatures decreases. Opening of the pseudogap in CeRhSb and CeRhAs enlarges the thermopower, and leads to the maxima of the thermoelectric figure of merit, 1.7×10−3 /K at 12 K and 1.0×10−3/K at 115 K, respectively. [Copyright &y& Elsevier]

We report on the temperature dependence of resistivity ρ, magnetic susceptibility χ, and specific heat under various pressures for the single crystal of an antiferromagnet Ce2Rh3Ge5. The Ne´el temperature TN disappears at Pc=0.45 GPa. For P>Pc, non-Fermi liquid behavior is observed in both ρ(T) and χ(T); ρ(T)=ρ0+ATn (n≅1.45) and χ(T)=χ0−DTm (m≅0.27). Even for P>3Pc, both n and m hardly change, i.e., no recovery of the Fermi-liquid state. Moreover, the Kondo temperature TK increases very weakly from 10 K at P=0 to 13 K at P=0.57 GPa. These findings indicate the important role of short-range magnetic correlations in the revised Doniach phase diagram. [Copyright &y& Elsevier]

Electrical resistivity ρ , magnetization M and specific heat C are reported for polycrystalline samples of the hexagonal system PrRh 3 . The magnetic susceptibility M / B obeys the Curie-Weiss law with the effective magnetic moment μ eff = 3.88 μ B /Pr and the paramagnetic Curie temperature θ p = +2.9 K, which indicates ferro-type magnetic interaction between the trivalent Pr ions. A cusp in C ( T ) at 3.0 K coincides with a bend in ρ ( T ). Applying magnetic fields, the peak broadens and shifts to higher temperatures. The field dependence indicates a ferro-type magnetic order. The magnetic entropy S m is (1/3) R ln2 at T C = 3.0 K, suggesting that part of the Pr ions take part in the magnetic order. A broad tail of the magnetic specific heat C m observed above T C may result from short-range correlations and/or fluctuations of the active magnetic dipole and quadrupoles in the ground state doublet. [ABSTRACT FROM AUTHOR]

PrIr 2 Zn 20 exhibits an antiferroquadrupolar (AFQ) order at T Q = 0.11 K, above which temperature the electrical resistivity ρ ( T ) shows an upward curvature and the magnetic specific heat divided by temperature C m / T follows − ln T dependence. The non-Fermi Liquid (NFL) behaviors have suggested formation of a quadrupole Kondo lattice. In the present work, we have studied the effect of Ga substitution for Zn on the NFL behavior by the measurements of the specific heat C , the magnetic susceptibility χ , and ρ of PrIr 2 Zn 20- x Ga x (0 ≤ x ≤ 0.25). With increasing x , the characteristic temperature T 0 defined as the temperature where the magnetic entropy S m reaches (3/4) R ln2 is increased by a factor of 3.5. Similarly, another characteristic temperature T R below which ρ ( T ) starts decreasing with the upward curvature increases with x by a factor of 1.2. The increments of both T 0 and T R may be attributed to the possible split of the Γ 3 doublet by symmetry lowering of the Pr sites. Otherwise, the quadrupole Kondo lattice would be stabilized by the enhanced c - f hybridization due to the increment of the 4 p electronic density and/or the chemical pressure effect. [ABSTRACT FROM AUTHOR]

Abstract: We report temperature dependent X-band () electron spin resonance (ESR) experiments in type-I clathrate . This system presents interesting thermoelectric properties in its paramagnetic state and orders ferromagnetically below . Although the ions sits on two inequivalent sites in the type-I clathrate structure, we found in the paramagnetic state a single Dysonian ESR line with a nearly temperature independent is observed, and its linewidth follows a Korringa-like behavior as a function of temperature. The microscopic details of the exchange coupling between the local moments and the conduction-electrons (c-e) in this compound are investigated through the obtained Korringa rate () and g-shift () from ESR experiments combined with the magnetic susceptibility and specific heat data. [Copyright &y& Elsevier]

Abstract: The spin dynamics of mixed-valence YbB has been studied by inelastic neutron scattering on a single crystal. In the Kondo-insulating regime, the spectra exhibit a spin-gap structure with two dispersive in-gap excitations at and 20meV. The lower mode is associated with short-range correlations near the antiferromagnetic wave vector . Its properties are in overall agreement with those expected for a “spin exciton” branch in the hybridization-gap picture, but Lu dilution experiments favor a more local mechanism for the gap formation. The vibrational behavior of Yb ions within the rigid B lattice is reflected into details of the phonon dispersion curves. [Copyright &y& Elsevier]

Abstract: The first microscopic investigation of superconductivity in LaNiSn is reported using muon spin rotation. LaNiSn is found to be mainly a type I superconductor in an intermediate state with some evidence for type II behaviour at low temperatures, possibly due to a temperature dependent Ginzburg Landau parameter . [Copyright &y& Elsevier]

Abstract: We report the measurements of magnetic susceptibility , specific heat C, electrical resistivity , and thermopower S of CeRhBi and CeIrSb, which are isostructural to the Kondo semimetal CeRhSb. For CeRhBi, C/T turns upward with decreasing temperature below 8K, and increases in proportion to down to 0.6K. Non-Fermi-liquid behavior appears also in (T) and (T); ) and ). These observations indicate that CeRhBi is a system located in the vicinity of a quantum critical point. CeIrSb, on the other hand, is classified as a valence fluctuating system from a large negative paramagnetic Curie temperature of and a broad maximum of S(T) at 130K. [Copyright &y& Elsevier]

Electrical-transport measurements of the semimetal CeBiPt in magnetic fields up to 60 T reveal a drastic change of the electronic band structure. The oscillating Shubnikov–de Haas signal vanishes above about 25 T although the quantum limit is not yet reached. Above this field the magnetoresistance rises strongly independent of angle and temperature. These unique features are caused by the Ce 4f electrons as evidenced by the absence of any unconventional behavior in the sister compound LaBiPt. [Copyright &y& Elsevier]

A detailed X-ray scattering study of the phase transitions in GdB6 has been performed. For photon energies away from resonance, peaks are observed with two distinct wave vectors of q1=(0 0 1/2) and q2=(1/21/20) at low temperatures. These are shown to arise from distortions of the lattice, although an earlier study had attributed them to competing magnetic-order parameters [J. Appl. Phys. 63 (1998) 3580]. With the photon energy tuned to the Gd L2 edge, a third set of peaks with q3=(1/41/41/2) and q2=(1/21/20) at low temperatures. These are shown to arise from distortions of the lattice, although an earlier study had attributed them to competing magnetic-order parameters [J. Appl. Phys. 63 (1998) 3580]. With the photon energy tuned to the Gd L2 edge, a third set of peaks with q3=(1/41/41/2 1/20) at low temperatures. These are shown to arise from distortions of the lattice, although an earlier study had attributed them to competing magnetic-order parameters [J. Appl. Phys. 63 (1998) 3580]. With the photon energy tuned to the Gd L2 edge, a third set of peaks with q3=(1/41/41/2 0) at low temperatures. These are shown to arise from distortions of the lattice, although an earlier study had attributed them to competing magnetic-order parameters [J. Appl. Phys. 63 (1998) 3580]. With the photon energy tuned to the Gd L2 edge, a third set of peaks with q3=(1/41/41/2 1/41/2 1/2) was discovered. This is shown to be the true magnetic-order parameter. Our results reveal a surprisingly rich interaction between the lattice and spin degrees of freedom in this compound. [Copyright &y& Elsevier]

Structural studies by means of powder X-ray diffraction and single-crystal neutron diffraction show that URhGe crystallizes in the orthorhombic TiNiSi-type of structure. Combined magnetic, electrical-transport and thermal studies performed for the first time on a single crystal confirm ferromagnetic order of URhGe below 9.6 K. In contrast to previous powder neutron-diffraction experiments, our single-crystal results point to collinear ferromagnetic order of U moments of 0.35±0.08 μB confined to the b–c plane, i.e. with no component along the a-axis, which is the hard-magnetization direction in URhGe. Our findings regarding the magnetic properties are in good agreement with theoretical first-principle calculations. [Copyright &y& Elsevier]

Abstract: Polycrystalline samples of a new rare-earth series RPd5Al2 crystallizing in the tetragonal ZrNi2Al5-type structure have been prepared. Their physical properties by electrical resistivity ρ, magnetic susceptibility χ, magnetization M and specific heat Cp measurements are reported. The ingots are composed of elongated grains preferentially aligned in the c direction; therefore, measurements were conducted parallel and perpendicular to the grains. Antiferromagnetic ordering appears in R=Ce, Nd, Gd, and Sm at low temperatures. CePd5Al2 has two AFM transitions at 4.1 and 2.9K and ρ(T) indicates a Kondo metal behavior with large anisotropy. In PrPd5Al2 no magnetic transition was observed down to 0.4K. The Cp (T) shows a broad peak around 13K due to the CEF effect, suggesting a non-magnetic singlet ground state. In NdPd5Al2, χ(T) shows anisotropy and the Cp (T) shows a sharp peak at 1.2K. The magnetic entropy at 3K is very close to Rln2, indicating a Kramers doublet ground state. In SmPd5Al2, Cp (T) shows a magnetic transition at 1.7K. Cp (T) for GdPd5Al2 shows a peak at 6K, followed by a broad anomaly around 3K. Within this series, T N''s for CePd5Al2 and NdPd5Al2 clearly deviate from the relation predicted by de Gennes scaling, which is ascribed to the CEF effect. [Copyright &y& Elsevier]

Abstract: We report on resistance and Hall-effect measurements of the half-Heusler compound CeBiPt in pulsed magnetic fields up to 70T. The band structure of the semimetal CeBiPt depends highly sensitively on temperature, magnetic field, and stoichiometry. This is reflected by the observed sample-dependent threshold fields above which the Shubnikov–de Haas signal disappears and at which clear changes of the Hall coefficient occur. [Copyright &y& Elsevier]

Abstract: The semimetallic half-Heusler alloy LaBiPt crystallizes in the non-centrosymmetric space group . We discovered superconductivity in this material below as evidenced by resistivity and magnetization measurements. The occurrence of superconductivity in LaBiPt is remarkable in view of its extremely low charge carrier concentration of . The charge carrier concentration is 1–2 orders of magnitude lower than in the classical low-carrier-density superconductors GeTe, SnTe and n-doped SrTiO3. [Copyright &y& Elsevier]

Abstract: Optical conductivity spectra [] have been measured for many heavy-fermion (HF) Ce and Yb compounds. A characteristic mid-infrared peak has been observed in of these compounds, and has been analyzed in terms of the conduction (c)-f electron hybridized bands. A universal scaling is found in terms of the observed peak energies for these HF compounds. This optical scaling is discussed in comparison with other universal relations found for HF compounds such as the Kadowaki–Woods relation. [Copyright &y& Elsevier]

Abstract: The temperature dependent optical conductivity spectrum of strontium filled skutterudites has been measured to investigate the origin of the heavy-fermion-like physical properties and the enhancement of the thermopower at around 50K. The optical conductivity spectra of and Ru at the temperature of 7K have peak structures at and 190meV, respectively. From the band structure calculation, the peaks correspond to the density of states (DOS) mainly originating from the Fe 3d and Ru 4d characters locating in the unoccupied states, i.e., has a very narrower band near the Fermi level than . The shape of DOS near is concluded to be the origin of the unconventional physical properties. [Copyright &y& Elsevier]

Abstract: Lattice dynamical properties of the type-I clathrate compounds of (, Sr, Ba) have been investigated by Raman scattering. We are successful in the assignment of the observed Raman active phonons to proper symmetry and are able to separate the guest atom origin modes from framework origin modes for the first time experimentally. From the measurements of temperature dependence of the guest origin peaks, we also demonstrate the difference of the behavior of the guest atom at high temperature and low temperature. [Copyright &y& Elsevier]

Abstract: We have carried out inelastic neutron scattering measurements on a Kondo insulator CeRhAs over a wide energy range. Our low-energy studies with an incident energy of do not show any evidence of magnetic scattering below 20meV. On the other hand, measurements done with exhibit a spin gap of 150meV. The spin gap energy of 150meV we found appears to be consistent with the Kondo temperature of estimated from bulk susceptibility. [Copyright &y& Elsevier]

Abstract: Magnetic properties of the alkaline earth filled skutterudite AFe4Sb12 , which are located in a proximity to a ferromagnetic instability, have been investigated by the high-field magnetization measurements in a pulsed magnetic field. At 1.3K, in CaFe4Sb12, a metamagnetic increase of magnetization appears at 13T where M reaches about . This metamagnetic anomaly weakens and the critical field shifts to a lower field in sequence of . The temperature variation of the metamagnetism has also been investigated, and the results are discussed in relation to the ferromagnetic instability. [Copyright &y& Elsevier]

Abstract: The structural, magnetic and thermal properties of Ce2Ge2In have been investigated between 0.36 and 300K. The specific heat exhibits a peak and the AC susceptibility exhibits a weak anomaly at 2K, whereas neutron diffraction does not show any signs of long-range magnetic ordering down to 0.36K. Inelastic neutron scattering at 17K shows two well-defined crystal field (CF) excitations at 11.6 and 20.1meV, indicating a doublet CF ground state of the Ce3+ ion in agreement with the entropy ∼Rln2 at 10K derived from the heat capacity data. [Copyright &y& Elsevier]

Abstract: We report bulk 4f and non-4f spectral functions near the Fermi level () of a Kondo semiconductor CeRhAs and its related compound CePdSn by virtue of high-resolution soft X-ray photoemission. The non-4f spectrum of CeRhAs measured at 20K shows a shoulder at the binding energy of and almost negligible spectral weight at . Although a peak similar to a tail of the Kondo resonance is observed in the 4f spectrum of CeRhAs, the intensity at is suppressed compared with those of metallic Ce compounds. These facts are attributed to signatures of the formation of a pseudo-gap in CeRhAs. [Copyright &y& Elsevier]

Abstract: CeBiPt is a low-carrier-density semimetal which exhibits antiferromagnetic ordering below . We measured the thermal expansivity down to 0.3K in zero and applied magnetic field . In , a peak in indicates the antiferromagnetic phase transition. Antiferromagnetic ordering is suppressed in low fields. With increasing field Zeeman splitting of the ground state appears. The low-energy thermal exitations are seen as a minimum in the temperature dependence of the longitudinal thermal expansivity. The magnetostriction, i.e. the relative length change as a function of B, reaches a large value of at . [Copyright &y& Elsevier]

Abstract: We report the measurements of electrical resistivity under various pressures for the single crystal of a heavy-fermion compound YbAgGe. This compound undergoes two magnetic phase transitions at (second order) and (first order). With applying pressure above 0.5GPa, the resistive anomalies at and merge into a sharp drop at . In the range , is constant, whereas the concomitant increase of suggests the development of spin fluctuations. For , largely decreases and the anomaly in becomes broader and shifts to higher temperatures. These significant changes at 1.5GPa suggest a transition from a small-moment ordered state to a stable magnetic state with suppressed spin fluctuations. [Copyright &y& Elsevier]

Abstract: We report the measurements of resistivity , specific heat C, and magnetization M on single crystals of the heavy-fermion weak-ferromagnet YbRhSb in various magnetic fields B as well as under pressures. Both the decrease of with increasing B and the peaking of at in modest fields confirm that the weak ferromagnetism is the consequence of canted antiferromagnetism. For , disappears at . Above , , C and M/B show a Fermi-liquid behavior. The results of under pressures reveal a broad maximum and a deep minimum of at 0.8 and 1.6GPa, respectively. This minimum suggests the competition of distinct-type of magnetic interactions. [Copyright &y& Elsevier]

We have measured the photoemission spectra of a Kondo insulator YbB12 (TK=220 K) by using synchrotron radiation at hν=700 eV to obtain the information on Yb 4f bulk electronic structures. On the fractured surface of the single crystal, the 4f peaks from the surface Yb2+ states are suppressed and the Yb3+ multiplet structures are well explained by the atomic multiplet calculation. We have also measured the temperature dependence of the spectra. The Yb3+ peaks are found to shift toward higher binding energies by 30 meV across Tmax (=75 K) as temperature is decreased. [Copyright &y& Elsevier]

The temperature dependences of the Yb 4f and 3d states of Kondo semiconductor YbB12 single crystal have been studied by high-resolution photoemission spectroscopy taken at hν=100 and 5951 eV. The Yb2+4f7/2 state at the Fermi level is enhanced on cooling. With improved energy resolution, we discover an additional quasi-particle peak at 15 meV that developes below 60 K. From the Yb 3d spectrum at 22 K, the Yb valence is estimated to be∼2.88. [Copyright &y& Elsevier]

Temperature dependence of Raman scattering spectra of Kondo insulator CeRhAs has been measured. With decreasing temperature, the phonon peaks split into doublet and triplet at about 370 K and below 165 K, respectively. The splitting is caused by a zone-folding due to the lattice modulations. The temperature dependence of the background intensity below 70 cm−1 is well explained by the resonance level model with V-shaped gap. [Copyright &y& Elsevier]

We have studied the inelastic neutron scattering from two Ce heavy fermion compounds, Ce(Ni0.935Cu0.065)Sn and Ce(Rh0.8Pd0.2)Sb, that are located at the magnetic–non-magnetic boundary. We find that the magnetic scattering follows a power law scaling behavior, and that the dynamical susceptibility, as deduced from the magnetic scattering, shows E/T scaling behavior with significantly different exponents for the two systems. [Copyright &y& Elsevier]

Ce7Ni3 orders antiferromagnetically near 2 K, but this ordering vanishes under pressure for Pc⩾ 0.32 GPa where the compound exhibits non Fermi liquid behavior. The μSR data on single crystals at ambient pressure give TN=1.85 K and reveal properties typical for a second order transition. Just above TN the paramagnetic spin fluctuations are non-isotropic confirming strong magnetic anisotropy. The μSR signal below TN is basically compatible with an incommensurate spin structure involving all Ce atoms having modulated moments primarily along the c-axis in agreement with neutron results. Details of the signal, however, indicate locally a more complex spin modulation. The maximum local field Bμ=0.15 T, confirms comparatively small Ce moments. The neutron data claim a second transition at TN=0.7 K, but the μSR signal shows no change around this temperature. If this transition exists at all, then the change in spatial arrangement of Ce spins must be very small. [Copyright &y& Elsevier]

We studied the effect of Ni incorporation on the magnetic properties of CeSbNix using resistivity, susceptibility, and magnetization measurements under high pressures and magnetic fields. With pressure, TN increases for CeSbNix with x⩽0.15. At the same time, pressure weakens a Cr-like anomaly found in the resistivity of CeSbNi0.08. While under high pressure bulk properties of CeSbNi0.08 are very similar to those of CeSb, the pressure dependence of the resistivity and magnetization of CeSbNi0.15 show different behavior. [Copyright &y& Elsevier]

Electron tunneling measurements have been carried out on the orthorhombic Kondo semiconductor CeRhAs using break junction. The measurements reveal the gap size 2Δ (4 K)=0.5±0.1 eV. This compound exhibits the susceptibility maximum at Tχ=510 K, below which the gap is believed to open. The gap ratio 2Δ/kBTχ=12±3 is consistent with that for the isostructural CeNiSn and CeRhSb, thereby indicating the same mechanism of the gap creation among the compounds. [Copyright &y& Elsevier]

We have measured the optical conductivity σ(ω) of CeNiSn, CeRhSb, and CeRhAs single crystals. The σ(ω) spectra exhibit a small pseudogap in the far infrared (IR) at low temperatures (T), and strongly T-dependent peaks in the mid-IR. The gap widths and the T-dependent variations are largest for CeRhAs and smallest for CeNiSn, well corresponding to their Kondo temperatures (TK’s), largest in CeRhAs (∼1300 K) and smallest in CeNiSn (∼40 K). The strong T dependence of σ(ω) in the mid-IR region suggests a strong c–f mixing in these compounds. The mid-IR peaks are very similar to spectral peaks previously reported for the mixed-valent compounds CeSn3 and CePd3. [Copyright &y& Elsevier]

Single crystals of Yb1−xLuxB12 (x=0,0.125,0.5,1) were measured between 1.8 and 300 K. We found similar spectral shapes in all compounds studied over the whole temperature range scanned. In zero field the spectra alter their appearance around 20, 100 and 150 K. In a longitudinal field of 100 G, which largely suppresses the contribution from 11B nuclear moments the relaxation rate remained constant up to ∼150 K where it suddenly peaks. These findings exclude magnetic correlations as the origin of muon spin relaxational behavior. The dominant features of the μSR spectra at low temperatures arise from lattice dynamics, probably involving the B12 clusters, rather than from spin dynamics. Higher temperature features are most likely muon related. [Copyright &y& Elsevier]

Abstract: High-resolution resonance-photoemission spectroscopy has been performed on the Ce1− x La x RhAs (0⩽x⩽0.05) single crystal to elucidate a collapse of the energy gap in the Kondo semiconductor CeRhAs by La substitution. With increasing x, the spectral intensity of the Ce4f1 derived states near the Fermi level decreases and new 4f derived spectral feature appears at a higher binding energy. The Rh4d-derived states, on the other hand, are not significantly changed by the substitution. New 4f-derived states have incoherent nature, which is responsible for the collapse of the semiconducting state for x>∼0.02. [Copyright &y& Elsevier]

Abstract: We report the measurements of magnetic and thermoelectric properties of Ba y Fe4− x Co x Sb12 (x=0, 1, 2, 2.5, 3). The host compound BaFe4Sb12 is a nearly ferromagnetic metal. With increasing x to 2.5, the resistivity increases by one order of magnitude and both the magnetic susceptibility and electronic specific heat coefficient decrease. A diamagnetic behavior for x=2.5 indicates that the Co substitution leads to a strong decrease of the electronic density of states near the Fermi level. The thermopower for x=0 exhibits local maximum at 50K, which disappears for x⩾1. A positive thermopower of 135μV/K at 500K for x=2.5 changes to a negative one, −120μV/K for x=3.0. This reversal of the sign indicates that the electron carries doped with the Co substitution overcompensates for the hole carriers in this system. [Copyright &y& Elsevier]

Abstract: The clathrate compound with the type-I cubic structure is expected to show the rattling motion of Sr atom which is an anomalous off-center oscillation. To investigate an influence of the rattling motion to the lattice system, we have measured temperature T dependence of elastic modulus and ultrasonic attenuation of a single-crystalline sample in the T range between 4.2 and 150K. We found a frequency dependence in and suggesting the rattling motion of Sr atoms between 20 and 60K. We obtained the relaxation time and the excitation energy 285K of the rattling motion. [Copyright &y& Elsevier]

Abstract: Tunneling measurements have been carried out on the Ba8Ga16Sn30. The break-junction was employed to obtain reliable tunneling spectra. The pseudo-gap like feature is obtained as 2Δ≈175meV, at 4.2K, which agrees with thermoelectric power data at low temperature. We have also obtained a small gap 2Δ≈30–40meV. [Copyright &y& Elsevier]

Abstract: Despite the fact that the only practical route to self-flux single crystal growth of Ba8Ga16Ge30 clathrates is through excess Ga flux, we have developed a method which results in p-type or n-type samples, depending on the relative Ge content in the starting mixture, and thus allows us to gain effective control over the charge carrier nature and density. An initial Ba:Ga:Ge ratio of 8:38:30 results in p-type crystals with average composition Ba8Ga16.6Ge29.4, while those grown from 8:38:34 initial ratio are n-type with average composition Ba8Ga15.9Ge30.1. More importantly, the thermopower S(T), resistivity ρ(T) and thermal conductivity κ(T) show radically different behaviors. The p-type crystals show: (i) monotonically increasing S(T) up to S(300K)≈+200μV/K, (ii) semiconducting ρ(T) (which decreases two orders of magnitude between 10 and 300K), and (iii) a glass-like low-temperature plateau in κ(T). In contrast, the n-type crystals show: (i) monotonically decreasing S(T) down to S(300K)≈−200μV/K, (ii) metallic ρ(T) in the 1–3mΩcm range, and (iii) a low-temperature crystalline peak in κ(T). [Copyright &y& Elsevier]

Abstract: The optical reflectivity spectra of clathrates Sr8Ga16Ge30 and β-Eu8Ga16Ge30 have been measured to investigate their electronic structure. A clear Drude shape was observed in the spectrum of Sr8Ga16Ge30. On the other hand, a broad Drude shape due to magnetic scattering by Eu 4f electrons and a peak originated from Eu 4f states were observed in the spectrum of β-Eu8Ga16Ge30. No clear change of optical conductivity due to the magnetic order was observed in β-Eu8Ga16Ge30 and no evidence of the rattling in Sr8Ga16Ge30 observed in contrast to α-Eu8Ga16Ge30. These results essentially originated from the large carrier density of these materials. [Copyright &y& Elsevier]

Abstract: The Ce 4f-derived states in CeRhX (X) were directly examined by means of high-resolution 3d–4f resonance photoemission spectroscopy. Compared with the Kondo metal CePtSn, which has a low Kondo temperature, CeRhX has a strong Ce 4f1 weight near the Fermi level (E F) and has a weak Ce 4f0 peak, indicating a strong valence fluctuation. The Ce 4f1 spectral features indicate that the c-f hybridization strength in CeRhSn is weaker than that in CeRhIn. [Copyright &y& Elsevier]

Abstract: Magnetization and neutron diffraction measurements on single crystal ErB4 have revealed that ErB4 orders antiferromagnetically below with an ordering vector . The magnetic susceptibility is highly anisotropic, . Successive metamagnetic transitions occur with a plateau at the half saturation magnetization (1/2 MS) for both B :italic>B gnetic phase diagram is presented and discussed in relation to the frustration of the Shastry–Sutherland lattice. [Copyright &y& Elsevier]

Abstract: We have measured the electrical resistivity , thermoelectric power S, and thermal conductivity in single-crystalline . La-substitution by 1% destroys the energy gap, suggesting that the coherence among the Ce-ions plays an important role for the semiconducting behavior. Within the investigated concentration range, the maximum power factor is found to be at room temperature. [Copyright &y& Elsevier]

The reflectivity of CeSbNi0.15 is measured at several temperatures in the low energy regions. The optical conductivity is obtained from the measured reflectivity. The carrier concentration and the relaxation time are evaluated by the Drude model. It is found that the p–f mixing collapse takes place in CeSbNi0.15 and that the gap formation occurs at 7 K. [Copyright &y& Elsevier]

Magnetoresistance measurements have been performed on CeNiSn at low temperatures down to 35 mK and in magnetic fields up to 20 T. Shubnikov-de Haas oscillations, observed for the first time, provide clear evidence that CeNiSn, formerly called a Kondo semiconductor, is a metal. The frequency and associated effective mass are 65 T and 13me for the field direction parallel to the crystallographic c-axis. [Copyright &y& Elsevier]

We have studied the evolution of energy gap in the optical conductivity [σ(ω)] of Yb1−xLuxB12 as functions of temperature (T) and non-magnetic Lu substitution (x). YbB12 has a well-developed energy gap in σ(ω) below 20 K, with the onset of σ(ω) at ∼20 meV and a shoulder at ∼40 meV. With increasing T or x, the energy gap is rapidly filled in, which indicates the importance of coherence among the Yb 4f orbitals at different sites. The shoulder, on the other hand, remains nearly unshifted in wide ranges of T (to 70 K @) and x (0–1/2), which shows that the characteristic energy for the gap is given by some single-site energy scale of Yb3+. Namely, both lattice and single-site effects play important roles in the gap formation of YbB12. [Copyright &y& Elsevier]