Two examples of a direct floating I_AB − V_AB characteristics recorded with the 2 initial set-up indicated when the sample was grounded. After setting up Tip A and Tip B distances to the Pb(111) surface, the sample was ungrounded. For this set up and for example in the symmetric set-up case I_A−GS  =  200 pA, I_B−GS  =  200 pA at 30 mV, it comes for the direct to the ground T_AS  =  0.8613 × 10⁻⁴ (for sample grounded) and T_BS  =  0.8613 × 10⁻⁴ (for sample grounded). The total transmission coefficient (leading to G in Eq. (1) via the Landauer formula) is T  =  0.4737 × 10⁻⁴ leading to T_AB < 0.043 × 10⁻⁴ (sample not grounded).