The discovery of superconductivity at 203 K in H3S 1 brought attention back to conventional superconductors whose properties can be described by the Bardeen-Cooper-Schrieffer (BCS) and the Migdal-Eliashberg theories. These theories predict that high, and even room temperature superconductivity (RTSC) is possible in metals possessing certain favorable parameters such as lattice vibrations at high frequencies. However, these general theories do not suffice to predict real superconductors. New superconducting materials can be predicted now with the aid of first principles calculations based on Density Functional Theory (DFT). In particular, the calculations suggested a new family of hydrides possessing a clathrate structure, where the host atom (Ca, Y, La) is at the center of the cage formed by hydrogen atoms 2-4 . For LaH10 and YH10 superconductivity, with critical temperatures Tc ranging between 240 and 320 K is predicted at megabar pressures 3-6 . Here, we report superconductivity with a record Tc  250 K within the Fm3m structure of LaH10 at a pressure P  170 GPa. We proved the existence of superconductivity at 250 K through the observation of zero-resistance, isotope effect, and the decrease of Tc under an external magnetic field, which suggests an upper critical magnetic field of 120 T at zerotemperature. The pressure dependence of the transition temperatures Tc (P) has a maximum of 250-252 K at the pressure of about 170 GPa. This leap, by  50 K, from the previous Tc record of 203 K 1 indicates the real possibility of achieving RTSC (that is at 273 K) in the near future at high pressures and the perspective of conventional superconductivity at ambient pressure.

One of the common features of unconventional superconducting systems such as the heavy-fermion, high transition-temperature cuprate and iron-pnictide superconductors is that the superconductivity emerges in the vicinity of long-range antiferromagnetically ordered state. In addition to doping charge carriers, the application of external pressure is an effective and clean approach to induce unconventional superconductivity near a magnetic quantum critical point. Here we report on the discovery of superconductivity on the verge of antiferromagnetic order in CrAs via the application of external pressure. Bulk superconductivity with T c E2 K emerges at the critical pressure P c E8 kbar, where the first-order antiferromagnetic transition at T N E265 K under ambient pressure is completely suppressed. The close proximity of superconductivity to an antiferromagnetic order suggests an unconventional pairing mechanism for CrAs. The present finding opens a new avenue for searching novel superconductors in the Cr and other transition metal-based systems.

X-ray absorption spectroscopy studies of the magnetic-insulating ground state of Sr2IrO4 at ambient pressure show a clear deviation from a strong spin-orbit (SO) limit J(eff)=1/2 state, a result of local exchange interactions and a nonzero tetragonal crystal field mixing SO split J(eff)=1/2, 3/2 states. X-ray magnetic circular dichroism measurements in a diamond anvil cell show a magnetic transition at a pressure of ∼17  GPa, where the "weak" ferromagnetic moment is quenched despite transport measurements showing insulating behavior to at least 40 GPa. The magnetic transition has implications for the origin of the insulating gap and the nature of exchange interactions in this SO coupled system. The expectation value of the angular part of the SO interaction, , extrapolates to zero at ∼80-90  GPa where an increased bandwidth strongly mixes J(eff)=1/2, 3/2 states and SO interactions no longer dominate the electronic ground state of Sr2IrO4.