G:=Alt(5);
H:=sub<G|[(1,2)(3,4),(1,3)(2,4)]>;
N:=Normaliser(G,H);
H_in_N:=sub<N|H>;
FAC,f:=quo<N|H_in_N>;
K:=GF(16);
dec:=DecompositionMatrix(FAC,K);

DecompositionMatrix(

G: GrpPerm: G, Degree 3, Order 3,
K: GF(2^4)
)

DecompositionMat(
G: GrpPerm: G, Degree 3, Order 3,
K: GF(2^4)
)
In file ".../Magma/package/RepThry/ModGrp/peakwords.m",
line 365, column 8:
>>   entry`decomp := sol;
          ^
Runtime error in :=: RHS value invalid for field 'decomp'
>