  The real Jacobi group $G^J_1(\mathbb{R})$, defined as the semi-direct product
of the group ${\rm SL}(2,\mathbb{R})$ with the Heisenberg group $H_1$, is
embedded in a $4\times 4$ matrix realisation of the group ${\rm
Sp}(2,\mathbb{R})$. The left-invariant one-forms on $G^J_1(\mathbb{R})$ and
their dual orthogonal left-invariant vector fields are calculated in the
S-coordinates $(x,y,\theta,p,q,\kappa)$, and a left-invariant metric depending
of 4 parameters $(\alpha,\beta,\gamma,\delta)$ is obtained. An invariant metric
depending of $(\alpha,\beta)$ in the variables $(x,y,\theta)$ on the Sasaki
manifold ${\rm SL}(2,\mathbb{R})$ is presented. The well known K&#228;hler
balanced metric in the variables $(x,y,p,q)$ of the four-dimensional
Siegel-Jacobi upper half-plane $\mathcal{X}^J_1=\frac{G^J_1(\mathbb{R})}{{\rm
SO}(2) \times\mathbb{R}} \approx\mathcal{X}_1 \times\mathbb{R}^2$ depending of
$(\alpha,\gamma)$ is written down as sum of the squares of four invariant
one-forms, where $\mathcal{X}_1$ denotes the Siegel upper half-plane. The
left-invariant metric in the variables $(x,y,p,q,\kappa)$ depending on
$(\alpha,\gamma,\delta)$ of a five-dimensional manifold
$\tilde{\mathcal{X}}^J_1= \frac{G^J_1(\mathbb{R})}{{\rm
SO}(2)}\approx\mathcal{X}_1\times\mathbb{R}^3$ is determined.
