  A good knowledge of the angular diameters of stars used to calibrate the
observables in stellar interferometry is fundamental. As the available
precision for giant stars is worse than the required per cent level, we aim to
improve the knowledge of many diameters using MATISSE (Multiple AperTure
mid-Infrared SpectroScopic Experiment) data in its different instrumental
configurations. Using the squared visibility MATISSE observable, we compute the
angular diameter value, which ensures the best-fitting curves, assuming an
intensity distribution of a uniform disc. We take into account that the
transfer function varies over the wavelength and is different from one
instrumental configuration to another. The uncertainties on the diameters are
estimated using the residual bootstrap method. Using the low spectral
resolution mode in the L band, we observed a set of 35 potential calibrators
selected in the Mid-infrared stellar Diameter and Flux Compilation Catalogue
with diameters ranging from about 1 to 3 mas. We reach a precision on the
diameter estimates in the range 0.6 per cent to 4.1 per cent. The study of the
stability of the transfer function in visibility over two nights makes us
confident in our results. In addition, we identify one star, 75 Vir initially
present in the calibrator lists, for which our method does not converge, and
prove to be a binary star. This leads us to the conclusion that our method is
actually necessary to improve the quality of the astrophysical results obtained
with MATISSE, and that it can be used as a useful tool for 'bad calibrator'
detection.
