Matrix t2*K(2) in Subspace 23 with Dimension 4

(K(2) is the second-order Grosse operator)

-5*t*U -(U^2/Sqrt[2]) 0 -((t*U)/Sqrt[2])
-(U^2/Sqrt[2]) (-7*t*U)/2 -((t*U)/Sqrt[2]) 0
0 -((t*U)/Sqrt[2]) -4*t*U U^2/Sqrt[2]
-((t*U)/Sqrt[2]) 0 U^2/Sqrt[2] (-11*t*U)/2