  Monovalent metals contain half filled band (HFB) of s-electrons. Emphasizing
importance of Coulomb repulsions in HFB in 2D and 1D monovalent systems we
sketched a theory (2018) for ambient temperature granular superconductivity
reported by Thapa and Pandey (2018) in Au-Ag nanostructures (updated by Thapa
et al., 2019). Sharpening our theory, we suggest that \textit{Coulomb
repulsions in certain structurally perturbed regions (atomic clusters, stacking
faults, grain boundaries etc.) create nanoscale reservoirs of singlet electron
pairs}. These low dimensional patches are hybridized to a background 3D jellium
metal and produce observed ambient Tc granular superconductivity via proximity
Josephson effect. Using repulsive Hubbard model we show presence of singlet
reservoirs and physics of doped Mott insulators. Needed charge transfer arises
from differing electronegativities. Our theory predicts that \textit{all
elemental monovalent (alkali, Cu, Ag and Au) metals, under suitable structural
perturbations, are likely to exhibit ambient temperature superconductivity}.
