Siunitx seems to typeset negative fractional powers differently depending on whether the \per command is used. MWE:







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Is there a setting which controls this, or is it a bug in siunitx?

  • 1
    Bug report inquiries should be sent to the package's maintainer.
    – Mico
    Commented Nov 4, 2023 at 17:40
  • \qty{4}{\per{\K\tothe{4/3}}} works for me
    – polyn
    Commented Nov 4, 2023 at 23:06
  • @polyn I didn't know about \qty, thanks! However for me \qty{4}{\per{\K\tothe{4/3}}} behaves as though there is no \per (giving K^{4/3}). I just updated the package - perhaps this is a bug. Commented Nov 5, 2023 at 0:42

1 Answer 1


At present, I can offer an explanation only. The code to work out negative powers does multiplication of the exponent as an expression. That means that -1 * (4/3) is evaluated here, which comes out as -1.333.... On the other hand, a \tothe power used alone is just printed as-is.

Likely a change would need some form of 'pretty printing' for fractional powers, so I need to consider that before any adjustment.

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