  The detection of lines in emission in planetary atmospheres provides direct
evidence of temperature inversion. We confirm the trend of ultra-hot Jupiters
orbiting A-type stars showing temperature inversions on their daysides, by
detecting metals emission lines in the dayside of KELT-20b. We first detect the
planetary emission by using the G2 stellar mask of the HARPS-N pipeline, which
is mainly composed of neutral iron lines, as a template. Using neutral iron
templates, we perform a retrieval of the atmospheric temperature-pressure
profile of the planet, confirming a thermal inversion. Then we create models of
planetary emission of different species using the retrieved inverted
temperature-pressure profile. By using the cross-correlation technique, we
detect FeI, FeII and CrI at signal-to-noise ratio levels of 7.1, 3.9 and 3.6,
respectively. The latter is detected for the first time in emission in the
atmosphere of an exoplanet. Contrary to FeI, FeII and CrI are detected only
after the occultation and not before, hinting for different atmospheric
properties in view on the pre- and post- occultation orbital phases. A further
retrieval of the temperature-pressure profile performed independently on the
pre- and post- occultation phases, while not highly significant, points to a
steeper thermal inversion in the post-occultation.
