Akm[k_,m_]:=Piecewise[{{0, (k != 4 && (k != 2 || m != 0)) || (m != -3 && m != 0 && m != 3)}, {(5*(Sqrt[21]*Mau2 + 2*Sqrt[14]*Meu))/21, k == 2 && m == 0}, {3*Sqrt[3/2]*(I*Mau1 + Mau3), k == 4 && m == -3}, {3*Sqrt[3/7]*Mau2 - (9*Meu)/Sqrt[14], k == 4 && m == 0}}, (3*I)*Sqrt[3/2]*(Mau1 + I*Mau3)]