Akm[k_,m_]:=Piecewise[{{(Eappxz + Eappyz + Eapx2y2 + Eapxy + Eapz2)/5, k == 0 && m == 0}, {0, (k != 4 && (k != 2 || (m != -2 && m != 0 && m != 2))) || (m != -4 && m != -2 && m != 0 && m != 2 && m != 4)}, {(Sqrt[3]*Eappxz - Sqrt[3]*Eappyz + (2*I)*Sqrt[3]*Mappyzxz - 4*Mapx2y2z2 - (4*I)*Mapz2xy)/(2*Sqrt[2]), k == 2 && m == -2}, {(Eappxz + Eappyz - 2*(Eapx2y2 + Eapxy - Eapz2))/2, k == 2 && m == 0}, {(Sqrt[3]*Eappxz - Sqrt[3]*Eappyz - (2*I)*Sqrt[3]*Mappyzxz - 4*Mapx2y2z2 + (4*I)*Mapz2xy)/(2*Sqrt[2]), k == 2 && m == 2}, {(3*Sqrt[7/10]*(Eapx2y2 - Eapxy + (2*I)*Mapx2y2xy))/2, k == 4 && m == -4}, {(3*(Eappxz - Eappyz + (2*I)*Mappyzxz + Sqrt[3]*Mapx2y2z2 + I*Sqrt[3]*Mapz2xy))/Sqrt[10], k == 4 && m == -2}, {(-3*(4*Eappxz + 4*Eappyz - Eapx2y2 - Eapxy - 6*Eapz2))/10, k == 4 && m == 0}, {(3*(Eappxz - Eappyz - (2*I)*Mappyzxz + Sqrt[3]*Mapx2y2z2 - I*Sqrt[3]*Mapz2xy))/Sqrt[10], k == 4 && m == 2}}, (3*Sqrt[7/10]*(Eapx2y2 - Eapxy - (2*I)*Mapx2y2xy))/2]