| A key question in condensed matter physics concerns whether pure three-dimensional metals can always be described as Fermi liquids. Our own interest in this field has been largely inspired by experimental studies of the cubic itinerant-electron helimagnet MnSi. I will review the mysteries related to this material and present recent experimental progress in our understanding of this compound. This includes in particular detailed studies of the magnetic structure and low lying excitations at ambient pressure by means of polarized and inelastic neutron scattering. Using the novel technique of neutron Larmor diffraction to overcome the traditional resolution limit of diffraction experiments, we also studied the lattice constants of MnSi at low temperatures and high pressures. We were able to resolve the nature of the pressure phase diagram of MnSi and establish that a stable, extended non-Fermi liquid state emerges under applied pressure without quantum criticality. |
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