  Using the publicly available eROSITA Final Equatorial Depth Survey (eFEDS)
data, we detected the stacked X-ray emissions at the position of 463 filaments
at a significance of 3.8 sigma based on the combination of all energy bands. In
parallel, we found that the probability of the measurement under the null
hypothesis is ~0.0017. The filaments were identified with galaxies in the Sloan
Digital Sky Survey survey, ranging from 30 Mpc to 100 Mpc in length at 0.2 < z
< 0.6. The stacking of the filaments was performed with the eFEDS X-ray
count-rate maps in the energy range between 0.4 - 2.3 keV after masking the
resolved galaxy groups and clusters and the identified X-ray point sources from
the ROSAT, Chandra, XMM-Newton, and eROSITA observations. In addition, diffuse
X-ray foreground and background emissions or any residual contribution were
removed by subtracting the signal in the region between 10 - 20 Mpc from the
filament spines. For the stacked signal, we performed an X-ray spectral
analysis, which indicated that the signal is associated with a thermal
emission. According to a model with the astrophysical plasma emission code for
the plasma emission and with a beta-model gas distribution with beta=2/3, the
detected X-ray signal can be interpreted as emission from hot gas in the
filaments with an average gas temperature of 1.0 (+0.3 -0.2) keV and a gas
overdensity of 21 +- 5 at the center of the filaments.
