The presence of MMBs in As-II is not only confirmed by the change of the pressure coefficient of the optical phonon frequencies and the high value of |γi| near Pt, but also by the high value of Z* (Fig. ). The high values of Z* (much higher than the nominal valence (0) of pure As) occur near Pt and also in the Ah phase, as it happens for IV-VI and V2-VI3 PCMs that are considered to be incipient metals . Additional confirmation of MMB formation in As-II comes from the pressure dependence of ∇ 2 ρ along the main bonds in the A7 and Ah phases (Fig. ). As expected, ∇ 2 ρ is negative for the strong primary covalent intralayer bond (d1 bond distance) and positive for the weak secondary interlayer bond (d2 bond distance) in As-I. Both ∇ 2 ρ values tend to equalize, especially above 15 GPa, until they reach a value close to zero above Pt. Notably, no classic bond is known to our knowledge to have simultaneously a ρ similar to that of covalent bonds (to be later discussed) and a ∇ 2 ρ close to zero . This seems only to happen for the MMB, as it was already shown for Sb-Te2 and Sn-Te2 bonds in crystalline SnSb2Te at RP and for Sb-Te and Ge-Te bonds in crystalline GST .