Abstract
We report the discovery of a spin-glass ground state in the transition-metal monosilicides with the B20 crystallographic structure. Magnetic, transport, neutron, and muon investigations of the solid solution Mn1-xCoxSi have revealed a new dome in the phase diagram with evidence of antiferromagnetic interactions. For Mn-rich compounds, a sharp decrease in the Curie temperature is observed upon Co doping and neutron elastic scattering shows that helimagnetic order of MnSi persists up to x=0.05 with a shortening of the helix period. For higher Co (0.05