We show that, given an almost-source algebra π΄ of a π-block of a finite group πΊ, then the unit group of π΄ contains a basis stabilized by the left and right multiplicative action of the defect group if and only if, in a sense to be made precise, certain relative multiplicities of local pointed groups are invariant with respect to the fusion system. We also show that, when πΊ is π-solvable, those two equivalent conditions hold for some almost-source algebra of the given π-block. One motive lies in the fact that, by a theorem of Linckelmann, if the two equivalent conditions hold for π΄, then any stable basis for π΄ is semicharacteristic for the fusion system.
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Barker et al. (2022) studied this question.