Highlights• Superconductivity in fcc-ThH10 at 159-161 K at the pressure 174 Gigapascals • Very wide interval of stability of fcc-ThH10 from 85 to 185 GPa. • Upper critical magnetic field ThH10 ~45 Т. • Novel discovered superhydride hcp-ThH9 with TC of 146 K (170 GPa) and upper critical field ~38 Т • Newly discovered thorium hydrides: I4/mmm-ThH4 and Cmc21-ThH6 Abstract Here we report targeted high-pressure synthesis of two novel high-TC hydride superconductors, P63/mmc-ThH9 and 3 ̅ -ThH10, with the experimental critical temperatures (TC) of 146 K and 159-161 K and upper critical magnetic fields (μHC) 38 and 45 Tesla at pressures 170-175 Gigapascals, respectively. Superconductivity was evidenced by the observation of zero resistance and a decrease of TC under external magnetic field up to 16 Tesla. This is one of the highest critical temperatures that has been achieved experimentally in any compounds, along with such materials as LaH10, H3S and HgBa2CaxCu2O6+z. Our experiments show that fcc-ThH10 has stabilization pressure of 85 GPa, making this material unique among all known high-TC metal polyhydrides. Two recently predicted Th-H compounds, I4/mmm-ThH4 (> 86 GPa) and Cmc21-ThH6 (86-104 GPa), were also synthesized. Equations of state of obtained thorium polyhydrides were measured and found to perfectly agree with the theoretical calculations. New phases were examined theoretically and their electronic, phonon, and superconducting properties were calculated.Graphical Abstract

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Neutron and x-ray powder and single crystal synchrotron diffraction of CsyFe2−xSe2 show the presence of superstructure reflections with propagation vector k=[ 2 5 , 1 5 , 1] with respect to the average crystal structure I4/mmm (a = 4, c = 15Å). The propagation vector star corresponds to the 5 times bigger unit cell given by transformation A=2a+b, B= -a+2b, C= c. A solution for the atomic structure is found in the space groups P 42/n and I4/m with an ordered pattern of iron vacancies corresponding to the iron deficiency x = 0.29 and Cs stoichiometry y = 0.83. The superstructure satellites are more pronounced in the neutron diffraction patterns suggesting that they can have some magnetic contribution. We have sorted out possible symmetry adapted magnetic configurations and found that the presence of AFM ordering with the ordered magnetic moment of Fe with 2µB does not contradict to the experimental data. However, the solutions space is highly degenerate and we cannot choose a specific solution. Instead we propose possible magnetic configurations with the Fe magnetic moments in (ab)-plane or along c-axis. The superstructure is destroyed above Ts 500 K by a first-order-like transition.PACS numbers: 75.50. Ee, 75.25.-j, 61.05.C-, 74.90.+n arXiv:1102

The presence of carbonates in inclusions in diamonds coming from depths exceeding 670 km are obvious evidence that carbonates exist in the Earth’s lower mantle. However, their range of stability, crystal structures and the thermodynamic conditions of the decarbonation processes remain poorly constrained. Here we investigate the behaviour of pure iron carbonate at pressures over 100 GPa and temperatures over 2,500 K using single-crystal X-ray diffraction and Mössbauer spectroscopy in laser-heated diamond anvil cells. On heating to temperatures of the Earth’s geotherm at pressures to ∼50 GPa FeCO3 partially dissociates to form various iron oxides. At higher pressures FeCO3 forms two new structures—tetrairon(III) orthocarbonate Fe43+C3O12, and diiron(II) diiron(III) tetracarbonate Fe22+Fe23+C4O13, both phases containing CO4 tetrahedra. Fe4C4O13 is stable at conditions along the entire geotherm to depths of at least 2,500 km, thus demonstrating that self-oxidation-reduction reactions can preserve carbonates in the Earth’s lower mantle.

We report on the synthesis of single crystals of BaFe(2)Se(3) and study their crystal and magnetic structures by means of synchrotron single-crystal x-ray and neutron powder diffraction. The crystal structure has orthorhombic symmetry and consists of double chains of FeSe(4) edge connected tetrahedra intercalated with barium. Below 240 K, long range spin-block checkerboard antiferromagnetic order is developed. The magnetic structure is similar to one observed in A(0.8)Fe(1.6)Se(2) (A = K, Rb or Cs) superconductors. The crystals exhibit a transition to the diamagnetic state with an onset transition temperature of T(c) ∼ 11 K. Though we observe FeSe as an impurity phase (<0.8% mass fraction) it is not likely that the diamagnetism is attributable to the FeSe superconductor, which has T(c) ≈ 8.5 K.