  By dealing with the evaluation of string theory correlators of $<V_C V_T
V_{\bar\Psi} V_\Psi>$, the complete and closed form of the amplitude of two
fermion fields, one tachyon and one closed string Ramond-Ramond field in type
IIB superstring theory is found. Specifically by comparing infinite tachyon
poles in field theory amplitude with infinite tachyon poles of the S-matrix of
string amplitude (for $p+1=n$ case), all the infinite higher derivative
corrections of two tachyons and two fermions (in type IIB) to all orders of
$\alpha'$ have been discovered. Using these new couplings, we are able to
produce infinite $t'+s'+u$-channel tachyon poles of string theory in field
theory. Due to internal degrees of freedom of fermions and tachyon (Chan-Paton
factors) we comment that, neither there should be single $s,t-$channel fermion
(tachyon pole) nor their infinite poles.
  Due to internal CP factor we also discover that there is no coupling between
two closed string Ramond-Ramond (RR) field and one tachyon in type II super
string theory.
  Taking into account the fact that the kinetic terms of fermions, gauge,
scalar fields and tachyons do not obtain any higher derivative corrections, and
due to their CP factors, string theory amplitude dictates us there should not
be any double poles in the amplitude of one RR, two fermions and one tachyon.
