Top left: MIDI UV coverage for the two sets of observations; labels 1, 2, 3 refer to B = 49.9 m, 54.8 m and 61.2 m, and labels 4, 5, 6 refer to B = 52.4 m, 56.1 m and 55.6 m (as detailed in Table 2). Top right: measured N-band visibilities of HD 139614 (with error bars) as a function of wavelength. We indicate the label (from 1 to 6) of each interferometric observation, as defined in Table 2. Bottom left: calibrated MIDI correlated flux measurements of HD 139614. We indicate the label (from 1 to 6) of each interferometric observation as defined in Table 2. Bottom right: averaged MIDI uncorrelated spectrum and Spitzer spectrum of HD 139614 between 8 μm and 13 μm. PAH emission features are visible at 8.6 μm and 11.3 μm, as detected by Acke et al. (2010).