Akm[k_,m_]:=Piecewise[{{(Ea + Eb1 + Eb2 + 2*Ee)/5, k == 0 && m == 0}, {Ea - Eb1 - Eb2 + Ee, k == 2 && m == 0}, {0, k != 4 || (m != -4 && m != 0 && m != 4)}, {(-3*Sqrt[7/10]*(Eb1 - Eb2 - (2*I)*Mb))/2, k == 4 && m == -4}, {(3*(6*Ea + Eb1 + Eb2 - 8*Ee))/10, k == 4 && m == 0}}, (-3*Sqrt[7/10]*(Eb1 - Eb2 + (2*I)*Mb))/2]