Ab initio band structure calculations are carried out for the higher borides MB 6 and MB 12 . Highprecision measurements of the elastic constants are performed for the compounds ZrB 12 , HoB 12 , ErB 12 , TmB 12 , LuB 12 , YB 6 and LaB 6 at low temperatures. The bulk properties of the borides are analyzed on the basis of the calculated equations of states and balanced crystal orbital overlap populations. Our calculations indicate that hexaborides with divalent metals, CaB 6 , SrB 6 , BaB 6 , and YbB 6 , are semiconductors with small energy gaps. The metallic MB 6 hexaborides with trivalent M atoms are found to possess larger bulk moduli values. For dodecaborides the bulk moduli are found to be higher for MB 12 with increased filling of the conduction band ͑ZrB 12 , HfB 12 , UB 12 ͒ in comparison with M 3+ B 12 compounds. The total energy calculations for different magnetic configurations in YbB 12 point to the possibility of antiferromagnetic coupling between Yb 3+ ions.

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The Fermi surface geometry and cyclotron masses of the antiferromagnet ErGa3 in a magnetic-field-induced paramagnetic phase are determined by using the de Haas-van Alphen effect method. The results are analysed on the basis of ab initio band-structure calculations and compared to corresponding results for the isostructural compounds TmGa3 and LuGa3.

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Magnetization studies for FeSe 1-x Te x (x 0, 0.5, and 1.0) compounds were carried out in magnetic fields up to 50 kOe and in the temperature range 2-300 K. The superconducting transition was observed at T c 8 K and 13.6-14.2 K in FeSe 0.963 and FeSe 0.5 Te 0.5 , respectively. For the most samples, a nonlinear behavior of the magnetization curves in the normal state gives evidence of a commonly observed substantial presence of ferromagnetic impurities in the compounds under study. By taking these impurity effects into account, the intrinsic magnetic susceptibility χ of FeSe 0.963 , FeSe 0.5 Te 0.5 , and FeTe was estimated to increase gradually with Te content. For FeTe a drastic drop in χ(T) with decreasing temperature was found at T N 70 K, which is presumably related to antiferromagnetic ordering. To shed light on the observed magnetic properties, ab initio calculations of the exchange enhanced magnetic susceptibility are performed for FeSe and FeTe within the local spin density approximation.

A paramagnetic response of transition metals and itinerant d-and f -metal compounds in an external magnetic field is studied by employing ab initio full-potential LMTO method in the framework of the local spin density approximation. Within this method the anisotropy of magnetic susceptibility in hexagonal close-packed transition metals is evaluated for the first time. This anisotropy is owing to the orbital Van Vleck-like paramagnetic susceptibility, which is revealed to be substantial in transition metal systems due to hybridization effects in electronic structure. It is demonstrated, that compounds TiCo, Ni 3 Al, YCo 2 , CeCo 2 , YNi 5 , LaNi 5 and CeNi 5 are strong paramagnets close to the quantum critical point. For these systems the Stoner approximation underestimates the spin susceptibility, whereas the calculated field-induced spin moments provided a good description of the large paramagnetic susceptibilities and magnetovolume effects. It is revealed, that itinerant description of hybridized f electrons produces magnetic properties of CeCo 2 , CeNi 5 , UAl 3 , UGa 3 , USi 3 and UGe 3 compounds in close agreement with experiment. In the uranium UX 3 compounds the strong spin-orbit coupling together with hybridization effects give rise to peculiar magnetic states, where the field-induced spin moments are antiparallel to the external field and the magnetic response is dominated by the orbital contribution.

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