Fig. 1. Neutron diffraction patterns of YCo5 at selected pressures, processed by the Rietveld method. The experimental points (red dots) and the calculated profiles (blue solid lines) are shown. The diffraction peaks include both nuclear and magnetic contributions and the ticks, below the calculated profile, indicate the peak positions. The position of extra peak from Al gasket of high-pressure cell is also shown.

Fig. 2. Pressure dependences of lattice parameters, a (red circles) and c (blue circles). The variation of the c/a ratio as a function of pressure is shown in the inset. The blue/red boxes represent the c and a values obtained by XRD at room temperature and ambient pressure.

Fig. 3. Temperature dependence of spontaneous magnetization at ambient pressure. Computed data: Red solid line - DMFT. The last few points of magnetization data (black squares) were fitted with $\sqrt{1-T/T_{c}}$ (blue circles). Single-crystal experiments of [23], green circles. Difference between single-crystal data (green circles) and powder sample (black squares) are consistent with previous findings [24].

Fig. 4. Spin-resolved total densities of states for LSDA (left) and LSDA + DMFT (right). Ambient pressure and p = 7.2 GPa are denoted by red dashed lines and blue solid lines, respectively. Arrows in the insets indicate the change in the position of flat bands.

Fig. 5. Band structure for ambient pressure (left) and p = 7.2 GPa (right) computed within the LSDA, including the spin-orbit coupling. Computed moments are oriented along the z-direction. Blue boxes and arrows indicate the position of flat bands.

Fig. 6. LDA + DMFT Bloch spectral function at 7.2 GPa, using U =2 eV and J = 0.9 eV. Red lines correspond to the LSDA band structure.

Fig. 7. Orbital magnetic moments of Co(2c)/(3 g) atom, at ambient pressure (red dashed) and at 7.2 GPa (blue solid), as a function of the Coulomb parameter U, for fixed J = 0.9 eV. Inset: ambient pressure results in comparison with those of Zhu et al. [17].

Fig. 8. Self-energies for the dxz-orbital at ambient pressure (dashed) and at p = 7.2 GPa (solid), for Co atoms at (2c/3g) site with red/blue lines. Inset (a) a reduced energy window around EF. Inset (b) effective mass renormalization, as function of U, at ambient pressure.