  We have established a plot of the anion height dependence of Tc for the
typical Fe-based superconductors. The plot appeared a symmetric curve with a
peak around 1.38 A. Both data at ambient pressure and under high pressure
obeyed the unique curve. This plot will be one of the key strategies for both
understanding the mechanism of Fe-based superconductivity and search for the
new Fe-based superconductors with higher Tc.
