The temperature-dependent zero-field 57Fe Mössbauer measurements on powders of 5e and 5e* (79.5 mg) were carried out with a standard WissEl and Halder transmission spectrometer and sinusoidal velocity sweep. The measurements between 80 K and 300 K were conducted on a CryoVac continuous-flow cryostat with He or N2 contact gas. After positioning the sample container (made of Teflon or PEEK), the sample chamber was evacuated, flushed six times with He or N2 gas, and kept at ca. 50 -100 mbar during the measurement. The temperature was measured with a calibrated silicon diode located close to the sample container, providing a temperature stability of better than ± 0.1 K. The nominal activity of the Fe Mössbauer source was 50 mCi of Co in a rhodium matrix, which was stored at ambient temperatures during the measurements. Velocity calibration was done with an α-Fe foil at 300 K; the minimum experimental line width (FWHM) was < 0.24 mm s -1 . Isomer shifts (δ) were specified relative to metallic Fe at ambient temperature but were not corrected in terms of the second-order Doppler shift. The spectra were analyzed by least-square fits using doublets of Lorentzian lines utilizing the software package NORMOS. Scanning electron microscopy (SEM) micrographs were taken on a Zeiss LEO 1530 GEMINI and a Zeiss Ultra plus. The acceleration voltage was set to 3 kV (with a Schottky-field-emission gun) using an in-lens secondary electron detector. The sample was sputter-coated with a 1.3 nm platinum layer.