File Name : figure_si_1.docx

Caption : samples after they stayed vertically into capillaries for saxs measurements.

File Name : figure_si_2.docx

Caption : fe k-edge xanes spectra of fe-om-ca aggregates and fe references used to perform linear combination fitting.

File Name : figure_si_3.docx

Caption : exafs spectra of fe(iii)-np (grey solid line), lcf results performing with fe(iii)-oligomer and fh (black dotted line) and the residual of the fit (black thin solid line).

File Name : figure_si_4.docx

Caption : saxs curves (black empty circles) and the modelled fe-pa form factor (red line) for all samples.

File Name : figure_si_5.docx

Caption : (a) apparent total structure factor st(q) for fe0.02-ca0.0 and (b) evolution of the peak representing the interaction between pa.

File Name : figure_si_6.docx

Caption : saxs curve (black) compared to sans curve with contrast at 50/50 h2o/d2o (blue).

File Name : figure_si_7.docx

Caption : sans curves with contrast at 100% d2o (black empty circles) and the guinier-porod modelling (red line) for all samples.

File Name : figure_si_8.docx

Caption : calcium k-edge exafs of fe-om-ca aggregates. grey solid lines are the experimental data and the black dotted lines are the fit results. 

File Name : figure_si_9.docx

Caption : magnitude and imaginary part of the ca k-edge exafs spectra fourier transform shell by shell fitting for sample fe0.05-ca0.5. experimental data are reported in grey solid line and the fit results are reported in black dotted line.

File Name : figure_si_10.docx

Caption : (a) exafs signal and (b) fourier transforms of calcite material. solid lines are experimental data and dotted lines are the fit results.