  Ultra-hot Jupiters are highly irradiated gas giants with equilibrium
temperatures typically higher than 2000K. Atmospheric studies of these planets
have shown that their transmission spectra are rich in metal lines, with some
of these metals being ionised due to the extreme temperatures. Here, we use two
transit observations of WASP-76b obtained with the CARMENES spectrograph to
study the atmosphere of this planet using high-resolution transmission
spectroscopy. Taking advantage of the two channels and the coverage of the red
and near-infrared wavelength ranges by CARMENES, we focus our analysis on the
study of the CaII infrared triplet (IRT) at 8500A and the HeI triplet at
10830A. We present the discovery of the CaII IRT at 7$\sigma$ in the atmosphere
of WASP-76b using the cross-correlation technique, which is consistent with
previous detections of the CaII H&K lines in the same planet, and with the
atmospheric studies of other ultra-hot Jupiters reported to date. The low mass
density of the planet, and our calculations of the XUV irradiation received by
the exoplanet, show that this planet is a potential candidate to have a HeI
evaporating envelope and, therefore, we performed further investigations
focussed on this aspect. The transmission spectrum around the HeI triplet shows
a broad and red-shifted absorption signal in both transit observations.
However, due to the strong telluric contamination around the HeI lines and the
relatively low signal-to-noise ratio of the observations, we are not able to
unambiguously conclude if the absorption is due to the presence of helium in
the atmosphere of WASP-76b, and we consider the result to be only an upper
limit. Finally, we revisit the transmission spectrum around other lines such as
NaI, LiI, H$\alpha$, and KI. The upper limits reported here for these lines are
consistent with previous studies.
