Akm[k_,m_]:=Piecewise[{{(Ea1x2y2 + Ea1z2 + Ea2 + Eb1 + Eb2)/5, k == 0 && m == 0}, {0, k == 1 && m == 0}, {(Sqrt[6]*Eb1 - Sqrt[6]*Eb2 - 4*Sqrt[2]*Ma1)/4, k == 2 && (m == -2 || m == 2)}, {(-2*Ea1x2y2 + 2*Ea1z2 - 2*Ea2 + Eb1 + Eb2)/2, k == 2 && m == 0}, {0, (k == 3 && (m == -2 || m == 2)) || (k == 3 && m == 0)}, {(3*Sqrt[7/10]*(Ea1x2y2 - Ea2))/2, k == 4 && (m == -4 || m == 4)}, {(3*(Eb1 - Eb2 + Sqrt[3]*Ma1))/Sqrt[10], k == 4 && (m == -2 || m == 2)}, {(3*(Ea1x2y2 + 6*Ea1z2 + Ea2 - 4*(Eb1 + Eb2)))/10, k == 4 && m == 0}}, 0]