Matrix t*K(1) in Subspace 88 with Dimension 12

(K(1) is the first-order Grosse operator)

I*Sqrt[3]*t (-I/2)*(-3*I + Sqrt[3])*U 0 0 0 0 0 0 0 0 0 0
((3 - I*Sqrt[3])*U)/2 (-I/2)*Sqrt[3]*t 0 Sqrt[3/2]*t 0 0 0 0 ((-3*I)*t)/Sqrt[2] 0 0 (Sqrt[3]*t)/2
0 0 0 0 (I*(I + Sqrt[3])*t)/Sqrt[2] 0 (I*(I + Sqrt[3])*t)/Sqrt[2] 0 0 ((1 - I*Sqrt[3])*t)/Sqrt[2] 0 0
0 -(Sqrt[3/2]*t) 0 0 -U 0 0 ((1 - I*Sqrt[3])*t)/Sqrt[2] -t (U - I*Sqrt[3]*U)/2 0 I*Sqrt[3/2]*t
0 0 ((1 + I*Sqrt[3])*t)/Sqrt[2] U 0 0 ((1 - I*Sqrt[3])*t)/2 0 (U + I*Sqrt[3]*U)/2 ((1 + I*Sqrt[3])*t)/2 (I*(I + Sqrt[3])*t)/Sqrt[2] 0
0 0 0 0 0 I*Sqrt[3]*t (-U - I*Sqrt[3]*U)/2 0 0 0 0 0
0 0 ((1 + I*Sqrt[3])*t)/Sqrt[2] 0 (-I/2)*(-I + Sqrt[3])*t (U - I*Sqrt[3]*U)/2 0 ((-1 - I*Sqrt[3])*U)/Sqrt[2] 0 (I/2)*(I + Sqrt[3])*t Sqrt[2]*t 0
0 0 0 ((-1 - I*Sqrt[3])*t)/Sqrt[2] 0 0 ((1 - I*Sqrt[3])*U)/Sqrt[2] 0 0 0 0 (1 + I*Sqrt[3])*t
0 ((-3*I)*t)/Sqrt[2] 0 t (I/2)*(I + Sqrt[3])*U 0 0 0 0 -U 0 t/Sqrt[2]
0 0 ((-1 - I*Sqrt[3])*t)/Sqrt[2] (-U - I*Sqrt[3]*U)/2 (I/2)*(I + Sqrt[3])*t 0 ((1 + I*Sqrt[3])*t)/2 0 U 0 ((1 + I*Sqrt[3])*t)/Sqrt[2] 0
0 0 0 0 ((1 + I*Sqrt[3])*t)/Sqrt[2] 0 -(Sqrt[2]*t) 0 0 (I*(I + Sqrt[3])*t)/Sqrt[2] (-I)*Sqrt[3]*t (I/2)*(I + Sqrt[3])*U
0 -(Sqrt[3]*t)/2 0 I*Sqrt[3/2]*t 0 0 0 (-1 + I*Sqrt[3])*t -(t/Sqrt[2]) 0 (U + I*Sqrt[3]*U)/2 (-I/2)*Sqrt[3]*t