High-spin states of odd-odd nucleus ${}^{138}\mathrm{Pm}$ are populated using the fusion-evaporation reaction ${}^{124}\mathrm{Te}({}^{19}\mathrm{F},5\mathrm{n}){}^{138}\mathrm{Pm}$. The previously known level scheme of ${}^{138}\mathrm{Pm}$ is extended and modified with the addition of nearly 40 new $\gamma$ transitions. One negative-parity band is newly established, and several new $E1$ transitions between the positive- and negative-parity bands are observed, indicating possible octupole correlations in ${}^{138}\mathrm{Pm}$. Two negative-parity bands before the back bend are assigned $\pi d_{5/2}\left[411\right]3/2^{+}\otimes \nu h_{11/2}\left[514\right]9/2^{-}$ and $\pi g_{7/2}\left[413\right]5/2^{+}\otimes \nu h_{11/2}\left[514\right]9/2^{-}$ configurations, which are interpreted as a pair of pseudospin partner bands, supported by the particle rotor model calculations. Moreover, the back bends observed in the two bands are attributed to the alignment of the first pair of $h_{11/2}$ protons. The previously observed negative-parity $\mathrm{\Delta }I=2$ band is extended to ${18}^{-}$ state, having a two-quasiparticle $\pi h_{11/2}\left[541\right]3/2^{-}\otimes \nu s_{1/2}$ configuration. In addition, a doubly decoupled band is identified and tentatively assigned the $\pi h_{11/2}\otimes \nu f_{7/2}$ configuration.

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• Collective levels
• Electromagnetic transitions
• Energy levels
• Fusion evaporation reactions
• Nuclear structure & decays
• 90 ≤ A ≤ 149