Measurements of the sound velocities, heat capacities, magnetic susceptibilities, and electrical resistivities of single crystals of MnSi, FeSi, and CoSi were performed in the temperature range 2.5\char21{}300 K and the elastic constants were calculated. The temperature dependence of the mentioned quantities reveals nontrivial features, reflecting specifics of magnetic and electron subsystems in these materials.

The dodecaboride ${\mathrm{LuB}}_{12}$ with cage-glass state and rattling modes has been studied to clarify the nature of the large amplitude vibrations of Lu ions. Discovered anisotropy of charge transport in conjunction with distortions of the conventional fcc symmetry of the crystal lattice may be attributed to coherent motion of Lu ions along a singular direction in the lattice. Arguments are presented in favor of cooperative dynamic Jahn-Teller effect in the boron sublattice to be the reason of the rattling mode, lattice distortion, and formation of the filamentary structure of the higher conducting channels—dynamic charge stripes.

High-quality single crystals of LuB ₁₂ are grown using the induction zone melting method. The x-ray data are collected at temperatures 293, 135, 95, 50 K. The crystal structure of LuB ₁₂ can be refined with record low R -factor in the cubic Fm m symmetry group despite reiterated observations of the cubic symmetry distortions both in the unit-cell values and in the physical properties. A peculiar computing strategy is developed to resolve this contradiction. True symmetry of the electron-density distribution in LuB ₁₂ is proved to be much lower than cubic as a result, which correlates very accurately with anisotropy of transport properties of LuB ₁₂ .

The itinerant helical ferromagnet $\mathrm{MnSi}$ reveals a number of remarkable features, which include tricritical phenomena at the phase transition line, Fermi-liquid breakdown, and so-called partial spin order in the paramagnetic state at high pressures. These features, probably interconnected, so far have no satisfactory explanations though several ideas have been suggested. Some current ideas focus on specifics of the spin fluctuations in the paramagnetic phase of $\mathrm{MnSi}$ close to the phase transition line. We report here the results of electrical resistivity measurements of a single crystal of $\mathrm{MnSi}$ across its ferromagnetic phase transition line at ambient and high pressures. Contrary to previous work in the field we made use of compressed helium as a pressure medium. Sharp peaks of the temperature coefficient of resistivity characterize the transition line. Analysis of these data shows that at pressures to $\sim 0.35\mathrm{GPa}$ these peaks have fine structure, revealing a shoulder at $\sim 0.5\mathrm{K}$ above the peak. That confirms the “abnormal” spin behavior in the narrow region above the Curie point and indicates the existence of a nontrivial fluctuation mode in the paramagnetic phase of $\mathrm{MnSi}$. It is symptomatic that this structure disappears at pressures higher than $\sim 0.35\mathrm{GPa}$, which was identified earlier as a tricritical point.

Spatial anisotropy generated spontaneously in the translationally invariant metallic phase, i.e. electron nematic effect, addresses a great challenge for both experimentalists and theoreticians. An interesting option for the realization of the electron nematic phase is provided by the system with orbital ordering, as long as both orbitally ordered states and electron nematic phases possess broken spatial symmetry. Here we report the detailed study of the angular dependences of the magnetoresistance in the orbitally ordered antiferroquadrupole (AFQ) phase of CeB₆. Our data allowed revealing the electron nematic effect, which develops when magnetic field exceeds a critical value of 0.3–0.5T. As a result, new transition inside the AFQ phase corresponding to the change of the symmetry of magnetic scattering on spin fluctuations in CeB₆ is discovered.

Electrical resistivity and magnetic susceptibility measurements of the itinerant ferromagnet ${\mathrm{CoS}}_2$ at high pressures reveal that its magnetic ordering temperature is tuned to zero at a critical pressure 4.8 GPa, indicating the existence of a quantum-phase transition. The ambient pressure continuous magnetic-phase transition in ${\mathrm{CoS}}_2$ becomes first order on a very slight pressure increase, with a tricritical point probably located almost at ambient pressure. No deviations from Fermi-liquid behavior were found in the vicinity of the quantum-phase transition in ${\mathrm{CoS}}_2$, implying its strong first-order nature.