  Using density functional theory, we calculated the formation energy of native
point defects (vacancies, interstitials and antisites) in MAX phase $Ti_2GeC$
and $Ti_3GeC_2$ compounds. Ge vacancy with formation energy of 2.87 eV was the
most stable defect in $Ti_2GeC$ while C vacancy with formation energy of 2.47
eV was the most stable defect in $Ti_3GeC_2$. Ge vacancies, in particular, were
found to be strong phonon scattering centres that reduce the lattice
contribution to thermal conductivity in $Ti_2GeC$. In both compounds, the
reported high thermal and electrical conductivity is attributed to the
electronic contribution that originates from the high density of states at the
Fermi level.
