How to use left over space in wpf tab items row - wpf

Question

Upper part of TabControl consists of TabItem controls. Is there a way to reuse remaining space there to put some WPF content?
I think I could use a "fake" TabItem with different styling and put my stuff in TabItem.Header but I was hoping there's a better way.
Solution
Based on the answer below, I got the desired behavior by wrapping TabPanel in the template below within e.g. StackPanel and adding my additional content after it.
<StackPanel Orientation="Horizontal">
<TabPanel
Grid.Row="0"
Panel.ZIndex="1"
Margin="0,0,4,-1"
IsItemsHost="True"
Background="Transparent" />
<TextBlock>Foo</TextBlock>
</StackPanel>

Answer 1

I tried a different way, which was to create another grid that occupies the same space as the TabControl, ie both are in Grid.Row=0. I have bound the grid height to the height of the first tab so if the tabs change height the other controls will remain centered. I set MinWidth on the window so the controls dont overlap the tabs.
Paste this code into a new WPF Window...
<Window x:Class="MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
mc:Ignorable="d"
Title="MainWindow" Height="306" Width="490" MinWidth="300">
<Grid>
<Grid.RowDefinitions>
<RowDefinition Height="*" />
<RowDefinition Height="Auto" />
</Grid.RowDefinitions>
<TabControl Grid.Row="0" x:Name="tabControl">
<TabItem x:Name="tabItem" Header="TabItem" Height="50">
<Grid Background="#FFE5E5E5"/>
</TabItem>
<TabItem Header="TabItem">
<Grid Background="#FFE5E5E5"/>
</TabItem>
</TabControl>
<Grid Grid.Row="0" Height="{Binding ActualHeight, ElementName=tabItem}"
VerticalAlignment="Top" Margin="0,2,0,0">
<StackPanel Orientation="Horizontal" HorizontalAlignment="Right"
VerticalAlignment="Center" Margin="20,0">
<TextBlock VerticalAlignment="Center" Margin="10,0" FontSize="16"
Foreground="Red" FontFamily="Calibri">My Text</TextBlock>
<Button Content="My Button" />
</StackPanel>
</Grid>
</Grid>
</Window>
...and you will get this:

Answer 2

You can use a template and make it do whatever you want, that is the power of WPF. Here is a nice article on customizing the TabControl and the TabItem controls.
< EDIT Adding code for TabControl template from Switch On The Code article>
<Style TargetType="{x:Type TabControl}">
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type TabControl}">
<Grid>
<Grid.RowDefinitions>
<RowDefinition Height="Auto"/>
<RowDefinition Height="*"/>
</Grid.RowDefinitions>
<TabPanel
Grid.Row="0"
Panel.ZIndex="1"
Margin="0,0,4,-1"
IsItemsHost="True"
Background="Transparent" />
<Border
Grid.Row="1"
BorderBrush="Black"
BorderThickness="1"
CornerRadius="0, 12, 12, 12" >
<Border.Background>
<LinearGradientBrush>
<GradientStop Color="LightBlue" Offset="0" />
<GradientStop Color="White" Offset="1" />
</LinearGradientBrush>
</Border.Background>
<ContentPresenter ContentSource="SelectedContent" />
</Border>
</Grid>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
all you have to do is add your content to the Template, the part that holds the tab items is the <TabControl>