Open a new tab in an existing browser session using Selenium

My current code below in C# opens a window then navigates to the specified URL after a button click.

protected void onboardButton_Click(object sender, EventArgs e)
{
   IWebDriver driver = new ChromeDriver();
   driver.FindElement(By.CssSelector("body")).SendKeys(Keys.Control + "t");
   driver.Navigate().GoToUrl("http://www.google.com")
}

But the site that I am planning to navigate to has single sign-on. How can I open a new tab in my existing browser session and navigate from there? The above code does not seem to work.