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# [Jelly], 9 bytes

    ŒHß¹Ḋ?€ZẎ

[Try it online!][TIO-knnjsy1w]

[Jelly]: https://github.com/DennisMitchell/jelly
[TIO-knnjsy1w]: https://tio.run/##y0rNyan8///oJI/D8w/tfLijy/5R05qoh7v6/h9u14z8/1/dOSQyyD9AXUdB3dU/0jnEzy8gyBPECwr1d/VzC3Z1dPMNcvEIUQcA "Jelly – Try It Online"

## How it works

    ŒHß¹Ḋ?€ZẎ - Main link f(S). Takes a string S on the left
    ŒH        - Split S into two halves
          €   - Over each half H:
         ?    -   If:
        Ḋ     -     Condition: H has more than 1 element
      ß       -     Then: yield f(H)
       ¹      -     Else: yield H
           Z  - Transpose the pair
            Ẏ - Dump inner lists