Singularity problem in integral3

Dear all,

I had an integral3 however, Matlab returned NaN and this warning: 'Non-finite result. The integration was unsuccessful. Singularity likely' Could you please help me? I also attached the file a.png for the function.

Thanks

d=37e-3;
l1=1e-3;
l2=1e-3;
n1=1;
n2=1;
mu=4*pi*1e-7;
a1=10.5e-3;
a2=10.5e-3;
b1=11.5e-3;
b2=11.5e-3;
fun_M=@(alp,r,y) (cos(alp.*d).*sin(alp.*l1/2).*sin(alp.*l2/2)./alp.^2) .* (r.*besselk(1,alp.*r)) .* (y.*besseli(1,alp.*y));
M=8*mu*n1*n2*integral3(fun_M,0,Inf,a1,b1,a2,b2,'AbsTol', 1e-12,'RelTol',1e-12)

[Torsten]

You will have a 0/0 problem for alp=0.

Best wishes

Torsten.