  Approximating the shape of the measured in $Bi_2Sr_2CaCu_2O_y$
magneto-thermopower (TEP) $\Delta S(T,H)$ by asymmetric linear triangle of the
form $\Delta S(T,H)\simeq S_p(H)\pm B^{\pm}(H)(T_c-T)$ with positive $B
^{-}(H)$ and $B ^{+}(H)$ defined below and above $T_c$, we observe that $B
^{+}(H)\simeq 2B ^{-}(H)$. In order to account for this asymmetry, we
explicitly introduce the field-dependent chemical potential of holes $\mu (H)$
into the Ginzburg-Landau theory and calculate both an average $\Delta
S_{av}(T,H)$ and fluctuation $\Delta S_{fl}(T,H)$ contributions to the total
magneto-TEP $\Delta S(T,H)$. As a result, we find a rather simple relationship
between the field-induced variation of the chemical potential in this material
and the above-mentioned magneto-TEP data around $T_c$, viz. $\Delta \mu
(H)\propto S_p(H)$.
