Let K be a knot in an integral homology 3-sphere Σ with exterior EK, and let B2 denote the two-fold branched cover of Σ branched along K. We construct a map Φ from the slice of trace-free SL2(ℂ)-characters of π1(EK) to the SL2(ℂ)-character variety of π1(B2). When this map is surjective, it describes the slice as the two-fold branched cover over the SL2(ℂ)-character variety of B2 with branched locus given by the abelian characters, whose preimage is precisely the set of metabelian characters. We show that each metabelian character can be represented as the character of a binary dihedral representation of π1(EK). The map Φ is shown to be surjective for all 2-bridge knots and all pretzel knots of type (p, q, r). An extension of this framework to n-fold branched covers is also described.
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