Akm[k_,m_]:=Piecewise[{{0, (k != 3 && k != 5) || (m != -2 && m != 2)}, {(Sqrt[7/2]*(I*Sqrt[5]*Ma1 + Sqrt[5]*Ma2 - 3*(Mb1 + I*Mb2)))/2, k == 3 && m == -2}, {(Sqrt[7/2]*((-I)*Sqrt[5]*Ma1 + Sqrt[5]*Ma2 - 3*Mb1 + (3*I)*Mb2))/2, k == 3 && m == 2}, {(11*(I*Ma1 + Ma2))/Sqrt[10], k == 5 && m == -2}}, (11*((-I)*Ma1 + Ma2))/Sqrt[10]]