Notes. Disc radius r_AD (Hennebelle et al. 2016) for different scenarios, with a fixed MRN dust distribution, accounting for coagulation only, coagulation and electrostatic repulsion, coagulation and erosion, coagulation-repulsion and a lower sticking efficiency (ϵ_stick = 0.5). The initial vertical magnetic field is assumed to be B_z = 30 μG, and the star-disc system mass to be M = 0.1 M_⊙. The ambipolar resistivity values η_AD are taken at the point of maximum departure from the MRN value, i.e. slightly before n_H = 10¹⁰ cm⁻³.