a, ARPES EDC profiles taken at the \(\bar{\Gamma }\)-point of MnBi 2 Te 4 (0001) at 10.5 K and 35 K. The raw data, resulting fitted curves, and their decompositions with Voigt peaks are shown by the coloured symbols, the black dashed lines, and the coloured lines and grey symbols, respectively. Red and blue lines (red circles and blue squares) indicate the peaks (EDCs) of the Dirac cone state at 35 K and 10.5 K, respectively. The peaks of the bulk bands at 35 K (10.5 K) are shown by grey circles (squares). b, Integrated intensity of the first two bulk conduction-band states (those analysed in detail in Extended Data Fig. 5c) as a function of temperature. Inset, The ARPES MnBi 2 Te 4 (0001) map measured with a laser photon energy of 6.4 eV and T = 10.5 K (as in Fig. 3d). The green rectangle marks the region of the map where the first two bulk conduction-band states are located. The average intensity in the shown temperature interval was set to 1. c, EDC profiles, N(E), taken at the \(\bar{\Gamma }\)-point between 10 K and 35 K with a temperature step ΔT ≈ 0.9 K and two sweep directions (10 K → 35 K→ 10 K). Because the measurements upon heating and cooling reveal essentially the same behaviour, in c we show the data averaged over these two sets of the EDC profiles at each temperature point. Note that the data in a and the intensity dependencies on temperature in b–d were acquired from two different B samples, showing slightly different binding energy of the Dirac point gap centres (0.28 eV and 0.25 eV, respectively). d, Intensity integrated within the energy window ΔE marked by the dashed black lines in c. The average intensity in the plateau-like region above approximately 24 K was set to 1. ΔE contains both the lower and upper parts of the Dirac cone at the \(\bar{\Gamma }\)-point and corresponds to the energy interval in which the contribution of the cone is dominant and that of the bulk states is almost negligible. The vertical cyan line approximately shows the start of the intensity increase, which roughly corresponds to T N ≈ 24 K for MnBi 2 Te 4 . e, The second derivative, d2N(E)/dE2, of the EDC profiles in c, shown for a clearer visualization of the Dirac point gap behaviour.